PSAT Math : PSAT Mathematics

Study concepts, example questions & explanations for PSAT Math

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Example Questions

Example Question #492 : Algebra

Solve for x:

Possible Answers:

6

9

8

11

10

Correct answer:

10

Explanation:

Combining the powers, we get 1024=2^{x}.

From here we can use logarithms, or simply guess and check to get x=10.

Example Question #13 : Exponents

If \dpi{100} \small r and \dpi{100} \small s are positive integers, and \dpi{100} \small 25\left ( 5^{r} \right )=5^{s-2}, then what is \dpi{100} \small s in terms of \dpi{100} \small r?

Possible Answers:

\dpi{100} \small r

\dpi{100} \small r+1

\dpi{100} \small r+2

\dpi{100} \small r+3

\dpi{100} \small r+4

Correct answer:

\dpi{100} \small r+4

Explanation:

\dpi{100} \small 25\left ( 5^{r} \right ) is equal to  which is equal to \dpi{100} \small \left ( 5^{r+2} \right ). If we compare this to the original equation we get \dpi{100} \small r+2=s-2\rightarrow s=r+4

Example Question #1111 : Psat Mathematics

If m and n are integers such that m < n < 0 and m2 – n2 = 7, which of the following can be the value of m + n?

            I. –5

           II. –7

          III. –9

Possible Answers:

II and III only

I only

I and II only

I, II and III only

II only

Correct answer:

II only

Explanation:

m and n are both less than zero and thus negative integers, giving us m2 and n2 as perfect squares. The only perfect squares with a difference of 7 is 16 – 9, therefore m = –4 and n = –3.

Example Question #1112 : Psat Mathematics

Possible Answers:

Correct answer:

Explanation:

To simplify, we can rewrite the numerator using a common exponential base.

Now, we can factor out the numerator.

The eights cancel to give us our final answer.

 

Example Question #1113 : Psat Mathematics

If , then what is ?

Possible Answers:

Correct answer:

Explanation:

Follow the order of operations by solving the expression within the parentheses first.

Return to solve the original expression.

 

Example Question #1114 : Psat Mathematics

Solve:

Possible Answers:

Correct answer:

Explanation:

 

Subtract the denominator exponent from the numerator's exponent, since they have the same base.

Example Question #1115 : Psat Mathematics

5/ 25 =

Possible Answers:

10

50

54 / 5

25

5

Correct answer:

25

Explanation:

25 = 5 * 5 = 52. Then 54 / 25 = 54 / 52

Now we can subtract the exponents because the operation is division. 54 / 5= 54 – 2 = 52 = 25. The answer is therefore 25.

Example Question #1 : How To Divide Exponents

For all real numbers n, (2n * 2) / (2n * 2n) =

Possible Answers:

2n

21 – n

2

2n/2n

2n – 1

Correct answer:

21 – n

Explanation:

(2n * 2) / (2n * 2n) simplifies to 2/2n or 21/2n.

When dividing exponents with the same base, you subtract the divisor from the dividend, giving 21–n.

Example Question #2 : How To Divide Exponents

 If x9/x3 = xn, solve for n.

Possible Answers:

6

9

12

7

3

Correct answer:

6

Explanation:

When dividing terms with the same base, we can subtract the exponents:

9 – 3 = 6

Example Question #3 : How To Divide Exponents

Simplify the following expression: (x2y4)/(x3y3z2)

Possible Answers:

y/xz2

z2xy

xy/z2

xz2/y

Correct answer:

y/xz2

Explanation:

According to the rules of exponents, ax/ay  = ax-y

In this expression, we can follow this rule to simplify x2/xand y4/y3

x2–3 = x–1 = 1/x. y4–3 = y1 = y.

Therefore, y/xz2 

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