Rewrite Exponential Expressions Using Exponents

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Algebra 2 › Rewrite Exponential Expressions Using Exponents

Questions 1 - 10
1

A savings account is modeled by $A(t)=A_0(1.06)^t$, where $t$ is in years. Which expression is equivalent and reveals the daily growth factor (assume 365 days per year) applied over $365t$ days?

$\left(\left(1.06\right)^{365}\right)^{t}$

$\left(\left(1.06\right)^{1/365}\right)^{365t}$

$\left(\left(1.06\right)^{1/365}\right)^{t}$

$\left(1.06\right)^{365t}$

Explanation

This question tests your ability to apply exponent properties to reveal daily growth factors from an annual model, adapting for finer time scales. Using the power-of-a-power rule $((b)^a$$)^c$ = b^(a c), we can rewrite $(1.06)^t$ as $((1.06)^{1/365}$$)^{365t}$, where $(1.06)^{1/365}$ is the daily factor that compounds 365 times to match the 6% annual growth. This daily factor is tiny, about 1.000159 or 0.0159% per day, but over 365t days it equals the original. The steps: (1) t years = 365t days, (2) Seek $(daily)^{365t}$, (3) Daily = $(1.06)^{1/365}$ since $((1.06)^{1/365}$$)^{365t}$ = $(1.06)^t$. Choice C correctly transforms to show the daily factor raised to 365t, as requested. Choice B uses $(1.06^{365}$$)^t$, which is like applying a huge yearly-overcompounded factor t times, not daily—remember to take the root for sub-periods! For daily or other frequent compounding, always use $(annual^{1/n}$$)^{n t}$ with n=365; approximate with a calculator if needed—this approach will serve you well in finance models, keep up the excellent work!

2

A quantity decays by 10% per year, modeled by $(0.90)^t$ after $t$ years. Rewrite $(0.90)^t$ to show an equivalent monthly decay factor applied over $12t$ months.

Which rewrite is correct?

$\left(\left(0.90\right)^{12t}\right)^{12}$

$\left(\left(0.90\right)^{1/12}\right)^{12t}$

$\left(\left(0.90\right)^{12}\right)^{t}$

$\left(0.90\right)^{t/12}$

Explanation

This question tests your use of exponent properties to convert a decay model from annual to monthly, highlighting equivalent forms for different periods. The power-of-a-power property $((b)^a$$)^c$ = b^(a c) allows rewriting $(0.90)^t$ as $((0.90)^{1/12}$$)^{12t}$, with $(0.90)^{1/12}$ as the monthly decay factor (about 0.9912, or 0.88% decay per month) applied over 12t months. This form shows monthly application while equaling the 10% annual decay. Steps: (1) t years = 12t months, (2) Want $(monthly)^{12t}$, (3) Monthly = $(0.90)^{1/12}$ since the exponents multiply to t. Choice B correctly applies this to reveal the monthly decay factor raised to 12t. Choice A uses $(0.90^{12}$$)^t$, which is like annual decay raised to t but overcompounded—take the root, not the power, for sub-periods! For decay models, the same rules apply: $(annual^{1/n}$$)^{n t}$ for n periods; this helps visualize gradual decline—fantastic effort, keep building on this!

3

An investment grows according to $A(t)=A_0(1.09)^t$, where $t$ is in years. Which expression is equivalent and uses exponent properties to show an approximate monthly growth model of the form $(\text{monthly factor})^{12t}$?

(You may use $1.09^{1/12}\approx 1.0072$.)

$A(t)=A_0,(1.0072)^{t}$

$A(t)=A_0,(1.0072)^{12t}$

$A(t)=A_0,(1.09)^{12t}$

$A(t)=A_0,(0.09)^{12t}$

Explanation

This question tests your ability to rewrite annual growth using exponent properties to approximate a monthly model, incorporating given numerical values. The power-of-a-power property lets us express $(1.09)^t$ as $((1.09)^{1/12}$$)^{12t}$, and with $1.09^{1/12}$ ≈ 1.0072, this becomes $(1.0072)^{12t}$, showing about 0.72% monthly growth over 12t months. This equivalent form reveals compounding at a monthly scale. Steps: (1) Use the rewrite $((1.09)^{1/12}$$)^{12t}$ = $(1.09)^t$, (2) Substitute the approximation for the monthly factor. Choice B correctly applies this with the given ≈1.0072 raised to 12t, matching the monthly model. Choice A uses $(1.0072)^t$, which understates growth by applying monthly factor yearly—ensure the exponent is n t for n periods! When approximations are provided, plug them into the property-based rewrite; this is key for real-world finance—excellent work, you're ready for more!

4

A culture of bacteria triples every day. If $t$ is measured in weeks, its growth factor can be written as $3^{7t}$ (since 7 days per week). Rewrite $3^{7t}$ using exponent properties as a power of a power so it looks like a weekly growth factor raised to $t$.

Which rewrite is correct?

$\left(3^{7t}\right)^{7}$

$\left(3^{1/7}\right)^{t}$

$\left(3^{t}\right)^{7}$

$\left(3^{7}\right)^{t}$

Explanation

This question tests your skill in rewriting exponential expressions using power-of-a-power to shift from daily to weekly growth factors while keeping the overall model equivalent. The property $(b^a$$)^c$ = b^(a c) lets us transform $3^{7t}$ (tripling every day over 7t days) into $(3^7$$)^t$, where $3^7$ is the weekly growth factor since seven daily triplings multiply to $3^7$, or 2187 times per week. This form emphasizes growth per week raised to t weeks, making it easier to think in weekly terms. To rewrite: (1) Identify the weekly factor as $(daily)^7$ = $3^7$, (2) Raise to t: $(3^7$$)^t$ = $3^{7t}$, confirming equivalence via the property. Choice B correctly applies this to show the weekly factor $3^7$ raised to t, matching the requested form. Choice C gives $(3^t$$)^7$ = $3^{7t}$ too, but it's raised to 7 instead of t, so it doesn't present as $weekly^t$—note the order matters for the interpretation! Use this strategy for any period change: group the base by the new time unit using exponents, and verify by expanding—you're mastering these conversions beautifully!

5

A population is modeled by $P(t)=P_0(1.08)^t$, where $t$ is in years. To express the same growth using quarters, rewrite $(1.08)^t$ as a quarterly factor raised to the number of quarters $4t$.

Which rewrite is correct?

$\left(\left(1.08\right)^{4t}\right)^{1/4}$

$\left(\left(1.08\right)^{4}\right)^{t/4}$

$\left(\left(1.08\right)^{1/4}\right)^{4t}$

$\left(1.08\right)^{t/4}$

Explanation

This question tests your ability to use exponent properties to rewrite exponential growth models for different time periods, such as converting annual to quarterly compounding. The power-of-a-power property $((b)^a$$)^c$ = b^(a c) enables us to express $(1.08)^t$ as $((1.08)^{1/4}$$)^{4t}$, where $(1.08)^{1/4}$ is the quarterly growth factor that, when applied four times per year, matches the annual 8% growth. The quarterly factor is approximately 1.0194, or about 1.94% per quarter, and this form highlights the growth over 4t quarters while remaining equivalent to the original expression. To make the conversion: (1) Note that t years equal 4t quarters, (2) Aim for (quarterly $factor)^{4t}$, (3) Set the quarterly factor to $(1.08)^{1/4}$ since $((1.08)^{1/4}$$)^{4t}$ = (1.08)^((1/4)*4t) = $(1.08)^t$, (4) Use a calculator to approximate if needed, (5) This systematically reveals the per-quarter rate. Choice A correctly uses the power-of-power property to show the quarterly factor raised to 4t, matching the requested form. A common mistake in Choice B is using $(1.08^4$$)^{t/4}$, which is mathematically equal but raises to t/4 instead of 4t, so it doesn't show the factor applied over the number of quarters—pay attention to the exponent matching the total periods! Remember the strategy: for n periods per year, rewrite $b^t$ as $(b^{1/n}$$)^{n t}$; this multiplies exponents to preserve equivalence and adapts to any time scale—great job exploring these transformations!

6

A bank advertises an annual growth factor of $1.15$. A student rewrites $$ (1.15)^t = \left((1.15)^{1/12}\right)^{12t} $$. What does this transformation reveal about the growth model (assume 12 months per year)?

The account grows by a constant monthly factor of $1.15/12$, applied over $12t$ months.

The account grows by 15% total over $12t$ months, not per year.

The account grows by 15% each month.

The account grows by a constant monthly factor of $(1.15)^{1/12}$, applied over $12t$ months.

Explanation

This question tests your understanding of how exponent properties reveal underlying growth rates in rewritten exponential expressions, like interpreting monthly compounding from an annual factor. The power-of-a-power property shows that $(1.15)^t = ((1.15)^{1/12})^{12t}$, where $(1.15)^{1/12}$ is the constant monthly growth factor applied over $12t$ months, equivalent to the annual 15% growth when compounded monthly. This monthly factor is approximately 1.0117, or about 1.17% per month, emphasizing compound growth rather than simple division. The transformation works because $((1.15)^{1/12})^{12t} = (1.15)^t$ via exponent multiplication, $(1/12) \times 12t = t$, and it reveals the per-month multiplier directly. Choice B correctly identifies that the rewrite shows a constant monthly factor of $(1.15)^{1/12}$ over $12t$ months, capturing the essence of compound interest. A tempting distractor like Choice C uses $1.15/12$, which is simple interest division (about 0.0958 or 9.58% monthly, way off), but compounding requires the root, not arithmetic division—watch for that mix-up! To interpret such rewrites, always check the inner exponent: $1/n$ for n periods per year gives the per-period factor; practice calculating these with a calculator to see how compounding boosts effective rates—you're building strong skills here!

7

A quantity decays by 10% per year, so its value after $t$ years is multiplied by $(0.90)^t$. Which expression correctly rewrites $(0.90)^t$ to show an equivalent daily factor raised to the number of days?

(Assume 365 days in a year.)

$(0.90)^t = \left((0.90)^{365}\right)^{t}$

$(0.90)^t = \left((0.90)^{1/365}\right)^{t/365}$

$(0.90)^t = \left((0.90)/365\right)^{365t}$

$(0.90)^t = \left((0.90)^{1/365}\right)^{365t}$

Explanation

This question tests your skills in using exponent properties to convert decay expressions to finer time scales, like daily from annual, even for decay factors less than 1. The power-of-a-power property $(b^a$$)^c$ = b^(a*c) allows rewriting $(0.90)^t$ as $((0.90)^{1/365}$$)^{365t}$, where $(0.90)^{1/365}$ is the daily decay factor—raised to 365t for total days in t years, equating back since (1/365)*365t = t, maintaining the same overall decay. To perform the rewrite: recognize t years ≈ 365t days, form (daily $factor)^{365t}$ with daily factor = $(0.90)^{1/365}$ via the property— this works for decay just as for growth, as exponents handle fractions and decimals fine. Choice B accurately applies the power-of-a-power property to create the daily equivalent with the correct exponent 365t. Choice C divides by 365 instead of taking the 365th root, which might tempt if confusing with simple rates, but for compounding decay, we need the root—division would give a linear approximation, not exponential! A transferable approach is: for n periods per unit time, use $(b^{1/n}$$)^{n t}$—verify by simplifying the exponent: (1/n)*n t = t. You're building strong skills; try this with weekly (n=52) to reinforce how the property systematically reveals per-period factors!

8

A tech company’s revenue is modeled by $R(t)=R_0,8^t$, where $t$ is in years. Rewrite $8^t$ in terms of base $2$.

(Use the power-of-power property.)

$8^t = 2^{3+t}$

$8^t = 2^{t/3}$

$8^t = 6^t$

$8^t = 2^{3t}$

Explanation

This question tests your ability to rewrite exponential expressions by changing the base using exponent properties, specifically for powers where the bases are related like 8 = $2^3$. The power-of-a-power property $(b^a$$)^c$ = b^(ac) lets us express $8^t$ as $(2^3$$)^t$ = $2^{3t}$, transforming the base while adjusting the exponent to keep equivalence— this reveals the growth in terms of doubling (base 2) tripled in exponent due to 8 being 2 cubed. To rewrite: factor the base $(8=2^3$), apply the property to multiply exponents: 3t = 3t, so $2^{3t}$ matches $8^t$ for any t— you can check with t=1: $8^1$=8, $2^{3}$=8. Choice C correctly uses the power-of-a-power property to convert to base 2 with the multiplied exponent 3t. Choice A divides the exponent by 3 instead of multiplying, a common slip when mixing up roots versus powers—remember, since 8 is 2 raised to 3, we multiply the exponent by 3, not divide! The strategy extends: for any b = $a^k$, then $b^t$ = $a^{k t}$ via power-of-a-power—practice with $9^t$ = $3^{?}$ (answer: 2t since $9=3^2$). Great job; this base-changing technique will help in many modeling problems, keep practicing!

9

A savings account has an annual growth factor of $1.15$. Which expression is equivalent to $(1.15)^t$ and makes the approximate monthly growth factor explicit?

(You may use a calculator for the approximation.)

$(1.15)^t = (1.012)^{12t}$ (monthly factor $\approx 1.012$)

$(1.15)^t = \left((1.15)^{1/12}\right)^{12t} \approx(1.0117)^{12t}$

$(1.15)^t = (1.15)^{12t}$

$(1.15)^t \approx(1.0123)^t$ (monthly factor $\approx 1.0123$)

Explanation

This question tests your ability to use exponent properties to rewrite exponential expressions in forms that make sub-period growth factors explicit, such as monthly from annual. The power-of-a-power property $(b^a$$)^c$ = b^(a*c) lets us express $(1.15)^t$ as $((1.15)^{1/12}$$)^{12t}$, where $(1.15)^{1/12}$ is the monthly factor—approximately 1.0117, meaning about 1.17% growth per month when compounded 12 times to match the 15% annual. To make the monthly factor explicit: identify that t years are 12t months, compute the 12th root of 1.15 using a calculator for ≈1.0117, and confirm $((1.0117))^{12t}$$(1.15)^t$ since the exponents multiply: (1/12)12t = t— this reveals the compounding structure without changing the value. Choice D correctly uses the power-of-a-power property to show the equivalent form and provides the accurate approximation for the monthly factor. Choice A uses a slightly off approximation (1.012 instead of 1.0117) and omits the root notation, which might come from mistakenly dividing the rate by 12 (15%/12=1.25%, then 1.0125 rounded) instead of taking the proper compound root—remember, simple division works for simple interest, but compounding requires the fractional exponent! The key strategy is to always take the nth root of the annual factor for n periods per year, then raise to (nt) for total periods—this ensures equivalence via exponent multiplication. You're doing great; try calculating $(1.15)^{1/12}$ yourself to see it's indeed ≈1.0117, and apply this to other periods like quarterly for more practice!

10

A population is modeled by $P(t)=P_0(1.08)^t$, where $t$ is in years. Rewrite the growth part $(1.08)^t$ to show an equivalent form with a quarterly growth factor raised to the number of quarters.

(Use the power-of-power property.)

$(1.08)^t = \left((1.08)^{1/t}\right)^{4}$

$(1.08)^t = \left((1.08)^{1/4}\right)^{4t}$

$(1.08)^t = \left((1.08)^{4}\right)^{t}$

$(1.08)^t = \left((1.08)^{1/4}\right)^{t/4}$

Explanation

This question tests your ability to apply exponent properties to rewrite growth expressions in terms of different time intervals, such as quarterly from annual. The power-of-a-power property $(b^a$$)^c$ = b^(a*c) enables us to transform $(1.08)^t$ into $((1.08)^{1/4}$$)^{4t}$, where $(1.08)^{1/4}$ is the quarterly factor—applied 4 times per year over t years, equaling 4t quarters, and both expressions match since (1/4)*4t = t. For the conversion: note t years = 4t quarters, seek (quarterly $factor)^{4t}$, set quarterly factor to $(1.08)^{1/4}$ so the property multiplies exponents back to t— you can verify with a calculator if needed, but the focus is on the algebraic equivalence. Choice A correctly implements the power-of-a-power property to produce the quarterly form with the exponent 4t for total quarters. Choice B reverses the process by raising to the 4th power inside, leading to $(1.08)^{4t}$, which overstates growth—a frequent error is confusing roots with powers, but remember to take the root (divide exponent) when breaking into more periods! To master this, use the formula: for m periods per year, rewrite $b^t$ as $(b^{1/m}$$)^{m t}$—the exponents multiply to t, preserving value. Keep up the excellent work; experiment with m=2 for semi-annual to see how this strategy transfers seamlessly!

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