PSAT Math : Algebra

Study concepts, example questions & explanations for PSAT Math

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Example Questions

Example Question #1 : How To Find Excluded Values

Which of the following provides the complete solution set for  ?

Possible Answers:

No solutions

Correct answer:

Explanation:

The absolute value will always be positive or 0, therefore all values of z will create a true statement as long as . Thus all values except for 2 will work.

Example Question #1 : How To Find Excluded Values

If the average (arithmetic mean) of , , and  is , what is the average of , , and ?

Possible Answers:

There is not enough information to determine the answer.

Correct answer:

Explanation:

If we can find the sum of \dpi{100} \small x+2, \dpi{100} \small y-6, and 10, we can determine their average. There is not enough information to solve for \dpi{100} \small x or \dpi{100} \small y individually, but we can find their sum, \dpi{100} \small x+y

Write out the average formula for the original three quantities.  Remember, adding together and dividing by the number of quantities gives the average: \frac{x + y + 9}{3} = 12

Isolate \dpi{100} \small x+y

x + y + 9 = 36

x + y = 27

 

Write out the average formula for the new three quantities: 

\frac{x + 2 + y - 6 + 10}{3} = ?

Combine the integers in the numerator:

\frac{x + y + 6}{3} = ?

Replace \dpi{100} \small x+y with 27:

\frac{27+ 6}{3} = \frac{33}{3} = 11

Example Question #2 : How To Find Excluded Values

Find the excluded values of the following algebraic fraction

Possible Answers:

The numerator cancels all the binomials in the denomniator so ther are no excluded values.

Correct answer:

Explanation:

To find the excluded values of a algebraic fraction you need to find when the denominator is zero. To find when the denominator is zero you need to factor it. This denominator factors into 

so this is zero when x=4,7 so our answer is 

Example Question #1 : How To Find Inverse Variation

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:

6

2

8

4

1

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 #604 : Algebra

 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 #3 : How To Find Inverse Variation

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 #1 : How To Find Inverse Variation

 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 #4 : How To Find Inverse Variation

 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 #5 : How To Find Inverse Variation

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

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