How to multiply variables - ISEE Upper Level Quantitative Reasoning
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Machine A can produce 4 buttons in 2 days. Machine B can produce 20 buttons in 4 days. How many buttons can Machine A and B, working together, produce in 40 days?
Machine A can produce 4 buttons in 2 days. Machine B can produce 20 buttons in 4 days. How many buttons can Machine A and B, working together, produce in 40 days?
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First determine how many buttons each machine can produce in a day.
Machine A: $\frac{4}{2}$=2 buttons per day
Machine B: $\frac{20}{4}$=5 buttons per day
Machine A and B can produce 7 buttons per day when they are working together.
7times 40=280 buttons
First determine how many buttons each machine can produce in a day.
Machine A: $\frac{4}{2}$=2 buttons per day
Machine B: $\frac{20}{4}$=5 buttons per day
Machine A and B can produce 7 buttons per day when they are working together.
7times 40=280 buttons
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Brian has 3 siblings. When his family orders pizza, each of the 4 children is given $\frac{1}{4}$ of the pizza. Brian does not feel well so he only finishes $\frac{1}{3}$ of his pizza. If the original pizza consisted of 12 slices of pizza, how many slices did Brian eat?
Brian has 3 siblings. When his family orders pizza, each of the 4 children is given $\frac{1}{4}$ of the pizza. Brian does not feel well so he only finishes $\frac{1}{3}$ of his pizza. If the original pizza consisted of 12 slices of pizza, how many slices did Brian eat?
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Brian eats $\frac{1}{3}$times $\frac{1}{4}$times 12 slices of pizza.
So Brian eats
$\frac{1}{12}$cdot 12=1 slice of pizza.
Brian eats $\frac{1}{3}$times $\frac{1}{4}$times 12 slices of pizza.
So Brian eats
$\frac{1}{12}$cdot 12=1 slice of pizza.
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Solve for x:
$\frac{1}{3}$x-14=7
Solve for x:
$\frac{1}{3}$x-14=7
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$\frac{1}{3}$x-14=7
$\frac{1}{3}$x-14+14=7+14
$\frac{1}{3}$x=21
3cdot $\frac{1}{3}$x=21cdot 3
x=63
$\frac{1}{3}$x-14=7
$\frac{1}{3}$x-14+14=7+14
$\frac{1}{3}$x=21
3cdot $\frac{1}{3}$x=21cdot 3
x=63
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Solve for x:
$4x^{2}$=256
Solve for x:
$4x^{2}$=256
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$4x^{2}$=256
$$\frac{4x^{2}$$}{4}=\frac{256}{4}$
$x^{2}$=64
$$\sqrt{x^{2}$$}=$\sqrt{64}$
x=pm 8
$4x^{2}$=256
$$\frac{4x^{2}$$}{4}=\frac{256}{4}$
$x^{2}$=64
$$\sqrt{x^{2}$$}=$\sqrt{64}$
x=pm 8
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Simplify:

Simplify:
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This can be solved using the pattern for the square of a difference:




This can be solved using the pattern for the square of a difference:
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Simplify:

Simplify:
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This can be solved using the pattern for the square of a sum:




This can be solved using the pattern for the square of a sum:
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Simplify:

Simplify:
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This can be solved using the pattern for the square of a sum:




This can be solved using the pattern for the square of a sum:
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Multiply:

Multiply:
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Use the FOIL method:





Use the FOIL method:
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Multiply:

Multiply:
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Define 
What is
?
Define
What is ?
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Substitute
for
:





Substitute for
:
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Simplify:

Simplify:
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First, recognize that raising the fraction to a negative power is the same as raising the inverted fraction to a positive power.

Apply the exponent within the parentheses and simplify. Remember that fractional exponents can be written as roots.

Simplify by taking the roots and canceling common factors.

First, recognize that raising the fraction to a negative power is the same as raising the inverted fraction to a positive power.
Apply the exponent within the parentheses and simplify. Remember that fractional exponents can be written as roots.
Simplify by taking the roots and canceling common factors.
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Simplify:

Simplify:
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First, recognize that raising the fraction to a negative power is the same as raising the inverted fraction to a positive power.

Apply the exponent within the parentheses and simplify. The negative in the fraction can be applied to either the numerator or the denominator, but not both; we will apply it to the numerator.


The fraction cannot be simplified further.
First, recognize that raising the fraction to a negative power is the same as raising the inverted fraction to a positive power.
Apply the exponent within the parentheses and simplify. The negative in the fraction can be applied to either the numerator or the denominator, but not both; we will apply it to the numerator.
The fraction cannot be simplified further.
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Simplify:

Simplify:
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Reorder the expression to group like-terms together.


Simplify by combining like-terms.


Reorder the expression to group like-terms together.
Simplify by combining like-terms.
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If the product of three consecutive numbers is 990, what is the smallest number?
If the product of three consecutive numbers is 990, what is the smallest number?
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If the product of three consecutive numbers is 990, then the smallest number can be found by plugging in each answer choice into the scenario to see whether it is correct.
If we plug in 9 as the smallest number, then the two consecutive numbers would be 10 and 11.
Given that 9 times 10 times 11 equals 990, that is the correct answer.
If the product of three consecutive numbers is 990, then the smallest number can be found by plugging in each answer choice into the scenario to see whether it is correct.
If we plug in 9 as the smallest number, then the two consecutive numbers would be 10 and 11.
Given that 9 times 10 times 11 equals 990, that is the correct answer.
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Megan teaches a cooking class. Every time a student takes a class, the student receives a 10% discount off of the price he paid for the previous class. The first class that Jose took cost $50. What will be the first class in which Jose pays less than $38?
Megan teaches a cooking class. Every time a student takes a class, the student receives a 10% discount off of the price he paid for the previous class. The first class that Jose took cost $50. What will be the first class in which Jose pays less than $38?
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In order to solve this problem, the price of $50 must be discounted by 10% until we get to a price of $38 or less.
The first class is 50.
The second class, being 10 percent less than the previous one, is 
The third class, being 10 percent less than the previous one, is 
The fourth class, being 10 percent less than the previous one, is 
Therefore, the answer is 4.
In order to solve this problem, the price of $50 must be discounted by 10% until we get to a price of $38 or less.
The first class is 50.
The second class, being 10 percent less than the previous one, is
The third class, being 10 percent less than the previous one, is
The fourth class, being 10 percent less than the previous one, is
Therefore, the answer is 4.
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If
is a positive number, what is a possible value of
?
If is a positive number, what is a possible value of
?
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If x is equal to
, then the equation could be written as follows:



Given that
is a positive number,
is a possible value of
.
If x is equal to , then the equation could be written as follows:
Given that is a positive number,
is a possible value of
.
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What is the simplified version of the expression below?

What is the simplified version of the expression below?
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The first step is to simplify the values in the parentheses:





The first step is to simplify the values in the parentheses:
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and
are both positive.
Evaluate
.
and
are both positive.
Evaluate .
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Multiply the binomials using the FOIL method - first, outer, inner, last - then combine like terms:




and
; also, by the Power of a Product Principle:
.
and
are both positive, so, substituting:
.
Again, using substitution:





Multiply the binomials using the FOIL method - first, outer, inner, last - then combine like terms:
and
; also, by the Power of a Product Principle:
.
and
are both positive, so, substituting:
.
Again, using substitution:
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Simplify the following expression

Simplify the following expression
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Simplify the following expression

Let's begin by multiplying our coefficients:

Next, we need to realize that we can combine our x's by adding the exponents.

Put it all together to get:

Simplify the following expression
Let's begin by multiplying our coefficients:
Next, we need to realize that we can combine our x's by adding the exponents.
Put it all together to get:
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Simplify the following:

Simplify the following:
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Simplify the following:

To begin, our coefficient will not change. We have just one integer (the 9) and nothing to multiply it by.
To combine our exponents, we will add them. This is because we are multiplying them


Put it together to get:

Simplify the following:
To begin, our coefficient will not change. We have just one integer (the 9) and nothing to multiply it by.
To combine our exponents, we will add them. This is because we are multiplying them
Put it together to get:
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