PSAT Math : PSAT Mathematics

Study concepts, example questions & explanations for PSAT Math

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Example Questions

Example Question #1151 : Psat Mathematics

Simplify:  2a^{2}b(ab^{2} - a^{2}b)\(\displaystyle 2a^{2}b(ab^{2} - a^{2}b)\)

Possible Answers:

2a^{3}b^{3} + a^{2}b^{2}\(\displaystyle 2a^{3}b^{3} + a^{2}b^{2}\)

2a^{2}b + 2a^{4}b^{2}\(\displaystyle 2a^{2}b + 2a^{4}b^{2}\)

2a^{3}b^{3} - 2a^{4}b^{2}\(\displaystyle 2a^{3}b^{3} - 2a^{4}b^{2}\)

2ab^{2} - 2a^{2}b\(\displaystyle 2ab^{2} - 2a^{2}b\)

ab^{2} - a^{2}b\(\displaystyle ab^{2} - a^{2}b\)

Correct answer:

2a^{3}b^{3} - 2a^{4}b^{2}\(\displaystyle 2a^{3}b^{3} - 2a^{4}b^{2}\)

Explanation:

Use the distributive property: a(b+c)=ab+ac\(\displaystyle a(b+c)=ab+ac\).  When we multiply variables with exponents, we keep the same base and add the exponents:  a^{m}a^{n} = a^{m+n}\(\displaystyle a^{m}a^{n} = a^{m+n}\)

Example Question #18 : Exponents

Simplify:

(6x^{2})^{2}\times y^{2} + xyz =\(\displaystyle (6x^{2})^{2}\times y^{2} + xyz =\)

Possible Answers:

\(\displaystyle 36x^{4}y^{2}+xyz\)

6x^{4}y^{2}z + xyz\(\displaystyle 6x^{4}y^{2}z + xyz\)

\(\displaystyle 36x^{5}y^{3}z\)

\(\displaystyle \textbf{cannot be simplified}\)

\(\displaystyle 36x^{4}y^{2}\)

Correct answer:

\(\displaystyle 36x^{4}y^{2}+xyz\)

Explanation:

(6x^{2})^{2} = 6^{2}x^{4} = 36x^{4}\(\displaystyle (6x^{2})^{2} = 6^{2}x^{4} = 36x^{4}\)

36x^{4}\times y^{2} = 36x^{4}y^{2}\(\displaystyle 36x^{4}\times y^{2} = 36x^{4}y^{2}\)

We cannot combine 36x^{4}y^{2}\(\displaystyle 36x^{4}y^{2}\) with xyz\(\displaystyle xyz\), so (6x^{2})^{2}\times y^{2} + xyz =36x^{4}y^{2}+xyz\(\displaystyle (6x^{2})^{2}\times y^{2} + xyz =36x^{4}y^{2}+xyz\).

Example Question #19 : Exponents

If \(\displaystyle c^2=15\), then what is the value of \(\displaystyle c^4\)?

Possible Answers:

\(\displaystyle 225\)

\(\displaystyle 125\)

\(\displaystyle 75\)

\(\displaystyle 110\)

\(\displaystyle \sqrt{15}\)

Correct answer:

\(\displaystyle 225\)

Explanation:

c4 is equal to (c2)(c2).

We know c2 = 15. Plugging in this value gives us c4 = (15)(15) = 225.

Example Question #20 : Exponents

If \(\displaystyle a\) and \(\displaystyle b\) are nonzero numbers such that \(\displaystyle a^2 = b^3\), which of the following is equivalent to \(\displaystyle a^6\)?

Possible Answers:

\(\displaystyle b^7\)

\(\displaystyle b^8\)

\(\displaystyle b^6\)

\(\displaystyle b^{11}\)

\(\displaystyle b^9\)

Correct answer:

\(\displaystyle b^9\)

Explanation:

For this problem, we need to make use of the property of exponents, which states that (xy)z = xyz.

We are given a2 but are asked to find a6.

Let's raise both sides of the equation to the third power, so that we will end up with a6 on the left side.

(a2)3 = (b3)3

Now, according to the property of exponents mentioned before, we can multiply the exponents. 

a(2*3) = b(3*3)

a6 = b9

The answer is b9.

Example Question #21 : Exponential Operations

If \(\displaystyle a\) and \(\displaystyle b\) are positive integers and \(\displaystyle 2^{2a}(2^{2b})=16\), what is the value of \(\displaystyle a +b\)?

Possible Answers:

\(\displaystyle 0\)

\(\displaystyle 3\)

\(\displaystyle -1\)

\(\displaystyle 1\)

\(\displaystyle 2\)

Correct answer:

\(\displaystyle 2\)

Explanation:

The question tells us that 22a ( 22b )= 16.

We can rewrite 16 as 24, giving us 22a ( 22b )= 24.

When terms with the same base are multipled, their exponents can be added:

2(2a +2b) = 24

Since the base is the same on both sides of the equation, we can equate the exponents:

2a +2b = 4

2(a + b) = 4

a + b = 2

Example Question #501 : Algebra

Simplify:

\(\displaystyle \left ( \frac{x}{2t^{2}} \right )^{3}\)

Possible Answers:

\(\displaystyle \frac{x^{3}}{ 8 t^{6} }\)

\(\displaystyle \frac{ 8 t^{6} }{x^{3}}\)

\(\displaystyle \frac{x^{3}}{ 6 t^{6} }\)

\(\displaystyle \frac{ 6 t^{6} }{x^{3}}\)

\(\displaystyle \frac{x^{3}}{ 9t^{6} }\)

Correct answer:

\(\displaystyle \frac{x^{3}}{ 8 t^{6} }\)

Explanation:

Apply the the various properties of exponents:

\(\displaystyle \left ( \frac{x}{2t^{2}} \right )^{3}\)

\(\displaystyle =\frac{x^{3}}{ \left ( 2t^{2} \right ) ^{3}}\)

\(\displaystyle =\frac{x^{3}}{ 2^{3} \left ( t^{2} \right )^{3} }\)

\(\displaystyle =\frac{x^{3}}{ 8 t^{2 \cdot 3} }\)

\(\displaystyle =\frac{x^{3}}{ 8 t^{6} }\)

 

Example Question #1155 : Psat Mathematics

\(\displaystyle \textup{If }4^{3}\times8^{2}=2^{y}\textup{, what is the value of }y\textup{ ?}\)

Possible Answers:

\(\displaystyle 10\)

\(\displaystyle 12\)

\(\displaystyle 16\)

\(\displaystyle 28\)

\(\displaystyle 6\)

Correct answer:

\(\displaystyle 12\)

Explanation:

\(\displaystyle \textup{4 and 8 are powers of 2. Find the common base and set exponents equal:}\)

\(\displaystyle \left ( 2^{2}\right )^{3}\times \left ( 2^{3}\right )^{2}=2^{y}\: \; \; \; \; \; \;2^{6}\times 2^{6}=2^{y}\)

\(\displaystyle 2^{12}=2^{y}\: \: \: \: \: \: \:12=y\)

Example Question #61 : Exponents

Simplify: \(\displaystyle x^{5}\cdot x^{2}\)

Possible Answers:

\(\displaystyle 2x^{7}\)

\(\displaystyle x^{7}\)

This expression cannot be simplified any further

\(\displaystyle x^{10}\)

\(\displaystyle 2x^{10}\)

Correct answer:

\(\displaystyle x^{7}\)

Explanation:

When you are multiplying and the bases are the same, you add the exponents together. Because both bases are \(\displaystyle x\) you add \(\displaystyle 5+2=7\) as your new exponent. You then keep the same base, \(\displaystyle x\), to the 7th power. 

Example Question #63 : How To Multiply Exponents

Solve for \(\displaystyle x\):

\(\displaystyle \sqrt[3]{x-3} = 2\)

 

Possible Answers:

\(\displaystyle None\ of\ the\ above\)

\(\displaystyle 5\)

\(\displaystyle 22\)

\(\displaystyle 11\)

\(\displaystyle 7\)

Correct answer:

\(\displaystyle 11\)

Explanation:

\(\displaystyle \left ( \sqrt[3]{x-3} \right )^{3} = 2^{3}\)

 

Now the left side equals \(\displaystyle x-3\) and the right side equals 8.  Hence:

\(\displaystyle x-3 = 8\)

Therefore \(\displaystyle x\) must be equal to 11.

Example Question #1152 : Psat Mathematics

Simplify the radical.

\sqrt{3283}\(\displaystyle \sqrt{3283}\)

Possible Answers:

7\sqrt{67}\(\displaystyle 7\sqrt{67}\)

67\sqrt{49}\(\displaystyle 67\sqrt{49}\)

57.3\(\displaystyle 57.3\)

56\(\displaystyle 56\)

7\sqrt{63}\(\displaystyle 7\sqrt{63}\)

Correct answer:

7\sqrt{67}\(\displaystyle 7\sqrt{67}\)

Explanation:

We can break the square root down into 2 roots of 67 and 49. 49 is a perfect square and reduces to 7.

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