PSAT Math : How to find inverse variation

Study concepts, example questions & explanations for PSAT Math

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Example Questions

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Example Question #12 : Algebraic Fractions

A school's tornado shelter has enough food to last 20 children for 6 days. If 24 children ended up taking shelter together, for how many fewer days will the food last?

Possible Answers:

1

4

8

2

6

Correct answer:

1

Explanation:

Because the number of days goes down as the number of children goes up, this problem type is inverse variation. We can solve this problem by the following steps:

20*6=24*x

120=24x

x=120/24

x=5

In this equation, x represents the total number of days that can be weathered by 24 students. This is down from the 6 days that 20 students could take shelter together. So the difference is 1 day less.

Example Question #1 : How To Find Inverse Variation

 varies inversely as the cube of .

If  when , then evaluate  when . (Nearest tenth)

Possible Answers:

 

Correct answer:

 

Explanation:

If  varies inversely as the cube of , then, if  are the initial values of the variables and  are the final values,

Substitute  and find :

This rounds to 2.3.

Example Question #14 : Algebraic Fractions

 varies inversely as the cube root of .

If  when , then evaluate  when . (Nearest tenth)

Possible Answers:

 

Correct answer:

Explanation:

If  varies inversely as the cube root of , then, if  are the initial values of the variables and  are the final values,

Substitute  and find :

Example Question #15 : Algebraic Fractions

Find the inverse of

 

Possible Answers:

Correct answer:

Explanation:

To find the inverse we first switch the x and y variables

Now we add 4 to each side

From here to isolate y we need to multiply each side by 2

By distributing the 2 we get our final solution:

Example Question #16 : Algebraic Fractions

 varies inversely as the square of .

If  when , then evaluate  when . (Nearest tenth)

Possible Answers:

Correct answer:

Explanation:

If  varies inversely as the square of , then, if  are the initial values of the variables and  are the final values,

.

Substitute  and find :

This rounds to 3.5.

Example Question #17 : Algebraic Fractions

 varies inversely with the square root of .

If  when , then evaluate  when . (Nearest tenth)

Possible Answers:

Correct answer:

Explanation:

If  varies inversely with the square root of , then, if  are the initial values of the variables and  are the final values,

.

Substitute  and find :

Example Question #21 : Algebraic Fractions

Find the inverse of .

Possible Answers:

Correct answer:

Explanation:

To find the inverse of a function we need to first switch the  and . Therefore,  becomes

We now solve for y by subtracting 1 from each side

From here we divide both sides by 2 which results in

Example Question #21 : Algebraic Fractions

Find the inverse of .

Possible Answers:

Correct answer:

Explanation:

To find the inverse we first switch the variables then solve for y.

Then we subtract  from each side

Now we divide by  to get our final answer. When we divide  by  we are left with . When we divide  by  we are left with . Thus resulting in:

Example Question #241 : Algebra

Find the inverse equation of:

 

Possible Answers:

Correct answer:

Explanation:

To solve for an inverse, we switch x and y and solve for y. Doing so yields:

 

 

Example Question #1 : How To Find Inverse Variation

Find the inverse equation of  .

Possible Answers:

Correct answer:

Explanation:

1. Switch the  and  variables in the above equation.

 

2. Solve for :

 

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