Rearranging Formulas to Highlight Quantities

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Algebra 2 › Rearranging Formulas to Highlight Quantities

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1

In finance, compound interest can be modeled by $A = P(1+r)^t$, where $A$ is final amount, $P$ is principal, $r$ is interest rate per period, and $t$ is the number of periods. Solve $A = P(1+r)^t$ for $P$.

$P = \dfrac{A}{1+rt}$

$P = A(1+r)^t$

$P = \dfrac{(1+r)^t}{A}$

$P = \dfrac{A}{(1+r)^t}$

Explanation

This question tests your ability to rearrange formulas to solve for a specific variable—essential for using formulas flexibly in science, engineering, and real-world problem-solving. Rearranging formulas with multiple variables works exactly like solving numeric equations, except the answer contains other variables instead of numbers: treat the variable you're solving for as the 'unknown x,' treat all other variables as 'known numbers,' then use inverse operations to isolate your target variable. Starting with A = P(1 + $r)^t$, divide both sides by (1 + $r)^t$ to isolate P, resulting in P = A / (1 + $r)^t$. Choice A correctly isolates P through division to get P = A / (1 + $r)^t$. A distractor like choice B might confuse it with solving for A instead, but always check which variable is the target. The formula rearrangement recipe: (1) Identify what you're solving for (that's your 'x'), (2) Identify what operation(s) are being done to that variable in the original formula, (3) Apply inverse operations in reverse order to isolate it (just like numeric equations!), (4) Simplify the result—combine fractions, simplify radicals, etc. You're building strong finance skills—keep going!

2

In physics, the kinematic equation $v^2 = u^2 + 2as$ relates final speed $v$, initial speed $u$, acceleration $a$, and displacement $s$. Solve $v^2 = u^2 + 2as$ for $a$ (treating the other variables as constants, as in solving a numeric equation).

$a = \dfrac{v^2-u^2}{2s}$

$a = \dfrac{2s}{v^2-u^2}$

$a = \dfrac{v^2-u^2}{s}$

$a = \dfrac{u^2-v^2}{2s}$

Explanation

This question tests your ability to rearrange formulas to solve for a specific variable—essential for using formulas flexibly in science, engineering, and real-world problem-solving. Rearranging formulas with multiple variables works exactly like solving numeric equations, except the answer contains other variables instead of numbers: treat the variable you're solving for as the 'unknown x,' treat all other variables as 'known numbers,' then use inverse operations to isolate your target variable. Starting with $v^2 = u^2 + 2as$, subtract $u^2$ from both sides to get $v^2 - u^2 = 2as$, then divide both sides by $2s$ to isolate a, resulting in $a = \dfrac{v^2 - u^2}{2s}$. Choice B correctly isolates a through subtraction and division to get $a = \dfrac{v^2 - u^2}{2s}$. A common distractor like choice C might forget to switch the signs when subtracting $u^2$, but remember that $v^2 - u^2$ is positive if v > u, so the order matters for the physics context. The formula rearrangement recipe: (1) Identify what you're solving for (that's your 'x'), (2) Identify what operation(s) are being done to that variable in the original formula, (3) Apply inverse operations in reverse order to isolate it (just like numeric equations!), (4) Simplify the result—combine fractions, simplify radicals, etc. Keep practicing these, and you'll master kinematic equations in no time!

3

In optics, thin lens relationships can be written as $\dfrac{1}{f} = \dfrac{1}{a} + \dfrac{1}{b}$, where $f$ is focal length and $a,b$ are distances. Rearrange $\dfrac{1}{f} = \dfrac{1}{a} + \dfrac{1}{b}$ to solve for $f$.

$f = \dfrac{a+b}{ab}$

$f = \dfrac{ab}{a-b}$

$f = \dfrac{a+b}{a-b}$

$f = \dfrac{ab}{a+b}$

Explanation

This question tests your ability to rearrange formulas to solve for a specific variable—essential for using formulas flexibly in science, engineering, and real-world problem-solving. More complex rearrangements may require advanced techniques: if your target variable is in a denominator (like 1/f in 1/f = 1/a + 1/b), you'll need to clear fractions first. Starting with 1/f = 1/a + 1/b, combine the right side over a common denominator to get 1/f = (a + b)/(ab), then take the reciprocal of both sides for f = ab/(a + b). Choice B correctly isolates f through combining fractions and taking the reciprocal to get f = ab/(a + b). A distractor like choice A might swap the reciprocal step, resulting in the inverse, but remember that reciprocating flips the equation correctly. The formula rearrangement recipe: (1) Identify what you're solving for (that's your 'x'), (2) Identify what operation(s) are being done to that variable in the original formula, (3) Apply inverse operations in reverse order to isolate it (just like numeric equations!), (4) Simplify the result—combine fractions, simplify radicals, etc. Great job tackling optics formulas—optics will feel intuitive soon!

4

In algebra-based modeling, suppose $y = \dfrac{kx}{x+a}$ where $a$ and $k$ are constants and $x\neq -a$. Solve $y = \dfrac{kx}{x+a}$ for $x$ in terms of $y, a, k$.

$x = \dfrac{y(k-a)}{k}$

$x = \dfrac{ya}{k-y}$

$x = \dfrac{ka}{k-y}$

$x = \dfrac{ya}{y-k}$

Explanation

This question tests your ability to rearrange formulas to solve for a specific variable—essential for using formulas flexibly in science, engineering, and real-world problem-solving. Watch for variables appearing multiple times: if your target variable appears in multiple places (like x in y = kx/(x + a)), factor it out first. Starting with y = kx/(x + a), multiply both sides by (x + a) to get y(x + a) = kx, expand to yx + ya = kx, then bring terms with x to one side: ya = kx - yx = x(k - y), so x = ya/(k - y). Choice A correctly isolates x through multiplication, rearrangement, and factoring to get x = ya/(k - y). A distractor like choice B might flip the denominator sign, but subtracting y from k keeps it positive assuming k > y. The formula rearrangement recipe: (1) Identify what you're solving for (that's your 'x'), (2) Identify what operation(s) are being done to that variable in the original formula, (3) Apply inverse operations in reverse order to isolate it (just like numeric equations!), (4) Simplify the result—combine fractions, simplify radicals, etc. You're mastering algebraic models—fantastic progress!

5

A projectile’s height might be modeled by a quadratic literal equation $h = ut - \dfrac{1}{2}gt^2$, where $h$ is height, $u$ is initial vertical velocity, $g$ is gravitational acceleration, and $t$ is time. Solve $h = ut - \dfrac{1}{2}gt^2$ for $t$.

$t = \dfrac{u \pm \sqrt{u^2 + 2gh}}{g}$

$t = \dfrac{u \pm \sqrt{u^2 - gh}}{2g}$

$t = \dfrac{u \pm \sqrt{u^2 - 2gh}}{g}$

$t = \dfrac{-u \pm \sqrt{u^2 - 2gh}}{g}$

Explanation

This question tests your ability to rearrange formulas to solve for a specific variable—essential for using formulas flexibly in science, engineering, and real-world problem-solving. More complex rearrangements may require advanced techniques: if your target variable appears with different powers (like t in h = ut - (1/2)gt²), you may need the quadratic formula! Rewrite as (1/2)gt² - ut + h = 0, then apply quadratic formula t = [u ± √(u² - 2gh)] / g, adjusting coefficients carefully. Choice A correctly isolates t using the quadratic formula to get t = (u ± √(u² - 2gh)) / g. A distractor like choice B might flip the sign on u, but in the standard arrangement, it's positive u for the linear term. Watch for variables appearing multiple times: if your target variable appears in multiple places (like t here), rearrange to standard quadratic form first. You're handling projectiles like a pro—keep practicing quadratics!

6

In geometry, the area of a triangle can be written as $A = \dfrac{1}{2}bh$, where $b$ is base and $h$ is height. Solve $A = \dfrac{1}{2}bh$ for $h$.

$h = \dfrac{A}{2b}$

$h = \dfrac{2A}{b}$

$h = 2Ab$

$h = \dfrac{b}{2A}$

Explanation

This question tests your ability to rearrange formulas to solve for a specific variable—essential for using formulas flexibly in science, engineering, and real-world problem-solving. Rearranging formulas with multiple variables works exactly like solving numeric equations, except the answer contains other variables instead of numbers: treat the variable you're solving for as the 'unknown x,' treat all other variables as 'known numbers,' then use inverse operations to isolate your target variable. Starting with A = (1/2)bh, multiply both sides by 2 to get 2A = bh, then divide by b to isolate h as h = 2A/b. Choice C correctly isolates h through multiplication and division to get h = 2A/b. A distractor like choice A might swap the 2 in the denominator, but multiplying by 2 clears the fraction properly. The formula rearrangement recipe: (1) Identify what you're solving for (that's your 'x'), (2) Identify what operation(s) are being done to that variable in the original formula, (3) Apply inverse operations in reverse order to isolate it (just like numeric equations!), (4) Simplify the result—combine fractions, simplify radicals, etc. Great foundation for geometry—keep building!

7

In physics, kinetic energy is $KE=\tfrac{1}{2}mv^2$, where $m$ is mass and $v$ is speed. Solve for $v$ in terms of $$KE$$ and $m$.

$v=\dfrac{2KE}{m}$

$v=\pm\sqrt{\dfrac{KE}{2m}}$

$v=\sqrt{\dfrac{m}{2KE}}$

$v=\pm\sqrt{\dfrac{2KE}{m}}$

Explanation

This question tests your ability to rearrange formulas to solve for a specific variable—essential for using formulas flexibly in science, engineering, and real-world problem-solving. Rearranging formulas with multiple variables works exactly like solving numeric equations, except the answer contains other variables instead of numbers: treat the variable you're solving for as the 'unknown x,' treat all other variables as 'known numbers,' then use inverse operations to isolate your target variable. The same algebraic moves apply—just keep everything symbolic! For example, solving $V = \pi r^2 h$ for r is like solving $100 = 3.14 \cdot r^2 \cdot 5$ for r: divide by $\pi$ and h, then take square root. More complex rearrangements may require advanced techniques: if your target variable is squared (like $r^2$ in $A = \pi r^2$), you'll need square roots ($r = \sqrt{\frac{A}{\pi}}$). If it appears in a denominator (like f in $1/f = 1/a + 1/b$), you'll need to clear fractions first. If it appears with different powers (like t in $s = ut + (1/2)at^2$), you may need the quadratic formula! The complexity of the rearrangement depends on how the variable appears in the formula. To solve $KE = (1/2)mv^2$ for v, first multiply both sides by $2/m$: $(2KE)/m = v^2$. Then take the square root: $v = \pm \sqrt{(2KE)/m}$. Choice B correctly isolates v through multiplying by the reciprocal and taking the square root with $\pm$ to get $v = \pm \sqrt{2KE/m}$. A common distractor like choice A fails by omitting the square root and the factor of 2, which leaves $v^2$ unresolved; include the $\pm$ for direction in physics contexts. The formula rearrangement recipe: (1) Identify what you're solving for (that's your 'x'), (2) Identify what operation(s) are being done to that variable in the original formula, (3) Apply inverse operations in reverse order to isolate it (just like numeric equations!), (4) Simplify the result—combine fractions, simplify radicals, etc. Example: $T = 2\pi \sqrt{L/g}$ solve for L: square both sides $\to T^2 = 4\pi^2 L/g$, multiply by g $\to gT^2 = 4\pi^2 L$, divide by $4\pi^2$ $\to L = gT^2/(4\pi^2)$. Each step undoes an operation! Watch for variables appearing multiple times: if your target variable appears in multiple places (like x in $xy + xz = w$), factor it out first: $x(y + z) = w$, then $x = w/(y + z)$. If you don't factor, you'll struggle to isolate! Also, when taking square roots of a variable, remember $\pm$ if the formula context allows both positive and negative (though often context restricts to positive only, like radius $r \geq 0$). Physics and geometry formulas usually want positive values only!

8

In physics, the kinematic relation $v^2=u^2+2as$ connects final speed $v$, initial speed $u$, acceleration $a$, and displacement $s$. Solve for $a$ in terms of $v$, $u$, and $s$.

$a=\dfrac{2s}{v^2-u^2}$

$a=\dfrac{u^2-v^2}{2s}$

$a=\dfrac{v^2-u^2}{2s}$

$a=\dfrac{v^2-u^2}{s}$

Explanation

This question tests your ability to rearrange formulas to solve for a specific variable—essential for using formulas flexibly in science, engineering, and real-world problem-solving. Rearranging formulas with multiple variables works exactly like solving numeric equations, except the answer contains other variables instead of numbers: treat the variable you're solving for as the 'unknown x,' treat all other variables as 'known numbers,' then use inverse operations to isolate your target variable. The same algebraic moves apply—just keep everything symbolic! For example, solving V = πr²h for r is like solving 100 = 3.14·r²·5 for r: divide by π and h, then take square root. More complex rearrangements may require advanced techniques: if your target variable is squared (like r² in A = πr²), you'll need square roots (r = √(A/π)). If it appears in a denominator (like f in 1/f = 1/a + 1/b), you'll need to clear fractions first. If it appears with different powers (like t in s = ut + (1/2)at²), you may need the quadratic formula! The complexity of the rearrangement depends on how the variable appears in the formula. To solve v² = u² + 2as for a, first subtract u²: v² - u² = 2as. Then divide by 2s: a = (v² - u²)/(2s). Choice A correctly isolates a through subtraction and division to get a = (v² - u²)/(2s). A common distractor like choice B fails by reversing the signs in the numerator, which would give negative acceleration incorrectly; preserve the order of subtraction. The formula rearrangement recipe: (1) Identify what you're solving for (that's your 'x'), (2) Identify what operation(s) are being done to that variable in the original formula, (3) Apply inverse operations in reverse order to isolate it (just like numeric equations!), (4) Simplify the result—combine fractions, simplify radicals, etc. Example: T = 2π√(L/g) solve for L: square both sides → T² = 4π²L/g, multiply by g → gT² = 4π²L, divide by 4π² → L = gT²/(4π²). Each step undoes an operation! Watch for variables appearing multiple times: if your target variable appears in multiple places (like x in xy + xz = w), factor it out first: x(y + z) = w, then x = w/(y + z). If you don't factor, you'll struggle to isolate! Also, when taking square roots of a variable, remember ± if the formula context allows both positive and negative (though often context restricts to positive only, like radius r ≥ 0). Physics and geometry formulas usually want positive values only!

9

A right circular cone has volume $V=\dfrac{1}{3}\pi r^2 h$, where $r$ is the radius and $h$ is the height. Solve for $r$ in terms of $V$ and $h$.

$r=\dfrac{3V}{\pi h}$

$r=\sqrt{\dfrac{\pi h}{3V}}$

$r=\pm\dfrac{3V}{\pi h}$

$r=\sqrt{\dfrac{3V}{\pi h}}$

Explanation

This question tests your ability to rearrange formulas to solve for a specific variable—essential for using formulas flexibly in science, engineering, and real-world problem-solving. Rearranging formulas with multiple variables works exactly like solving numeric equations, except the answer contains other variables instead of numbers: treat the variable you're solving for as the 'unknown x,' treat all other variables as 'known numbers,' then use inverse operations to isolate your target variable. The same algebraic moves apply—just keep everything symbolic! For example, solving V = πr²h for r is like solving 100 = 3.14·r²·5 for r: divide by π and h, then take square root. More complex rearrangements may require advanced techniques: if your target variable is squared (like r² in A = πr²), you'll need square roots (r = √(A/π)). If it appears in a denominator (like f in 1/f = 1/a + 1/b), you'll need to clear fractions first. If it appears with different powers (like t in s = ut + (1/2)at²), you may need the quadratic formula! The complexity of the rearrangement depends on how the variable appears in the formula. To solve V = (1/3)πr²h for r, first multiply both sides by 3/πh to isolate r²: (3V)/(πh) = r². Then take the square root: r = √((3V)/(πh)). Choice B correctly isolates r through multiplying by the reciprocal and taking the square root to get r = √(3V/(πh)). A common distractor like choice A fails by omitting the square root, leaving r² unaddressed; always apply the inverse of the power. The formula rearrangement recipe: (1) Identify what you're solving for (that's your 'x'), (2) Identify what operation(s) are being done to that variable in the original formula, (3) Apply inverse operations in reverse order to isolate it (just like numeric equations!), (4) Simplify the result—combine fractions, simplify radicals, etc. Example: T = 2π√(L/g) solve for L: square both sides → T² = 4π²L/g, multiply by g → gT² = 4π²L, divide by 4π² → L = gT²/(4π²). Each step undoes an operation! Watch for variables appearing multiple times: if your target variable appears in multiple places (like x in xy + xz = w), factor it out first: x(y + z) = w, then x = w/(y + z). If you don't factor, you'll struggle to isolate! Also, when taking square roots of a variable, remember ± if the formula context allows both positive and negative (though often context restricts to positive only, like radius r ≥ 0). Physics and geometry formulas usually want positive values only!

10

In chemistry, the ideal gas law is $PV=nRT$, where $P$ is pressure, $V$ is volume, $n$ is moles, $R$ is a constant, and $T$ is temperature. Solve for $T$ in terms of $P$, $V$, $n$, and $R$.

$T=\dfrac{PV}{nR}$

$T=\dfrac{nR}{PV}$

$T=\dfrac{P}{nRV}$

$T=\dfrac{PR}{nV}$

Explanation

This question tests your ability to rearrange formulas to solve for a specific variable—essential for using formulas flexibly in science, engineering, and real-world problem-solving. Rearranging formulas with multiple variables works exactly like solving numeric equations, except the answer contains other variables instead of numbers: treat the variable you're solving for as the 'unknown x,' treat all other variables as 'known numbers,' then use inverse operations to isolate your target variable. The same algebraic moves apply—just keep everything symbolic! For example, solving V = πr²h for r is like solving 100 = 3.14·r²·5 for r: divide by π and h, then take square root. More complex rearrangements may require advanced techniques: if your target variable is squared (like r² in A = πr²), you'll need square roots (r = √(A/π)). If it appears in a denominator (like f in 1/f = 1/a + 1/b), you'll need to clear fractions first. If it appears with different powers (like t in s = ut + (1/2)at²), you may need the quadratic formula! The complexity of the rearrangement depends on how the variable appears in the formula. To solve PV = nRT for T, divide both sides by nR: T = PV/(nR). Choice B correctly isolates T through division by nR to get T = PV/(nR). A common distractor like choice A fails by inverting the fraction incorrectly, which would not isolate T properly; ensure you divide by the coefficients multiplying T. The formula rearrangement recipe: (1) Identify what you're solving for (that's your 'x'), (2) Identify what operation(s) are being done to that variable in the original formula, (3) Apply inverse operations in reverse order to isolate it (just like numeric equations!), (4) Simplify the result—combine fractions, simplify radicals, etc. Example: T = 2π√(L/g) solve for L: square both sides → T² = 4π²L/g, multiply by g → gT² = 4π²L, divide by 4π² → L = gT²/(4π²). Each step undoes an operation! Watch for variables appearing multiple times: if your target variable appears in multiple places (like x in xy + xz = w), factor it out first: x(y + z) = w, then x = w/(y + z). If you don't factor, you'll struggle to isolate! Also, when taking square roots of a variable, remember ± if the formula context allows both positive and negative (though often context restricts to positive only, like radius r ≥ 0). Physics and geometry formulas usually want positive values only!

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