PSAT Math : How to find the square of an integer

Study concepts, example questions & explanations for PSAT Math

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Example Questions

Example Question #1 : How To Find The Square Of An Integer

Simplify. 

Possible Answers:

Correct answer:

Explanation:

Take the square root of both the top and bottom terms.

Simplify. 

Example Question #21 : Square Roots And Operations

The square root of 5184 is:

Possible Answers:

71

70

72

74

73

Correct answer:

72

Explanation:

The easiest way to narrow down a square root from a list is to look at the last number on the squared number – in this case 4 – and compare it to the last number of the answer. 

70 * 70 will equal XXX0

71 * 71 will equal XXX1

72 * 72  will equal XXX4

73 * 73 will equal XXX9

74 * 74  will equal XXX(1)6

Therefore 72 is the answer.  Check by multiplying it out.

Example Question #22 : Square Roots And Operations

If 5^{x}+5^{x}+5^{x}+5^{x}+5^{x}=5^{10}, what is the value of x?

Possible Answers:

1

10

5

9

2

Correct answer:

9

Explanation:

5(5^{x})=5^{10}

5^{1}(5^{x})=5^{10}

5^{x+1}=5^{10}

x=9

Example Question #3 : How To Find The Square Of An Integer

If x and y are integers and xy + y2 is even, which of the following statements must be true?

I. 3y is odd

II. y/2 is an integer

III. xy is even

Possible Answers:

I, II, & III

I only

I & II 

II only

Correct answer:

Explanation:

In order for the original statement to be true, the  and  terms must be either both odd or both even. Looking at each of the statements individually,

I. States that  is odd, but only odd values multiplied by 3 are odd. If  was an even number, the result would be even. But can be either odd or even, depending on what equals. Thus this statement COULD be true but does not HAVE to be true.

II. States that  is an integer, and since only even numbers are cleanly divided by 2 (odd values result in a fraction) this ensures that  is even. However, can also be odd, so this is a statement that COULD be true but does not HAVE to be true.

III. For exponents, only the base value determines whether it is even or odd - it does not indicate the value of y at all. Only even numbers raised to any power are even, thus, this ensures that  is even. But can be odd as well, so this statement COULD be true but does not HAVE to be true.

An example of two integers that will work violate conditions II and III is and .

, and even number.

is not an integer.

is not even.

Furthermore, any combination of 2 even integers will make the original statement true, and violate the Statement I.

Example Question #2 : How To Find The Square Of An Integer

How many integers from 20 to 80, inclusive, are NOT the square of another integer?

Possible Answers:

Correct answer:

Explanation:

First list all the integers between 20 and 80 that are squares of another integer:

52 = 25

62 = 36

72 = 49

82 = 64

In total, there are 61 integers from 20 to 80, inclusive. 61 – 4 = 57

Example Question #24 : Square Roots And Operations

Let the universal set  be the set of all positive integers.

Let  be the set of all multiples of 3; let  be the set of all multiples of 7; let  be the set of all perfect square integers. Which of the following statements is true of 243?

Note:  means "the complement of ", etc.

Possible Answers:

Correct answer:

Explanation:

, so 243 is divisible by 3. .

, so 243 is not divisible by 7.  - that is, .

, 243 is not a perfect square integer.  - that is, .

Since 243 is an element of , and , it is an element of their intersection. The correct choice is that

Example Question #25 : Square Roots And Operations

Consider the inequality:

Which of the following could be a value of ?

Possible Answers:

x=-\frac{4}{3}

x=-\frac{3}{4}

x=1

x=-1

There is no possible value for x

Correct answer:

x=-\frac{3}{4}

Explanation:

Notice how x^4 is the greatest value. This often means that x is negative as (-1)^n=-1 when \dpi{100} n is odd and (-1)^n=1 when \dpi{100} n is even.

Let us examine the first choice, x=-\frac{3}{4}

x^5=-\frac{3^5}{4^5}=-\frac{243}{1024}> -\frac{3}{4}

This can only be true of a negative value that lies between zero and one.

Example Question #26 : Square Roots And Operations

In the equation above, if  is a positive integer, what is the value of ?

Possible Answers:

Correct answer:

Explanation:

Begin by squaring both sides of the equation:

Now solve for y:

Note that  must be positive as defined in the original question. In this case,  must be 12.

 

 

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