ISEE Middle Level Quantitative : How to find the square root

Study concepts, example questions & explanations for ISEE Middle Level Quantitative

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Example Questions

Example Question #1 : How To Find The Square Root

Give the square root of 256.

Possible Answers:

\displaystyle 14

\displaystyle 18

\displaystyle 24

\displaystyle 22

\displaystyle 16

Correct answer:

\displaystyle 16

Explanation:

\displaystyle 16\cdot16= 256 - that is, 16 squared is 256, making 16 the square root of 256 by definition.

Example Question #2 : How To Find The Square Root

Which is the greater quantity?

(a) \displaystyle \sqrt{425 }

(b) \displaystyle 21

Possible Answers:

(a) and (b) are equal

(b) is greater

It is impossible to tell from the information given

(a) is greater

Correct answer:

(b) is greater

Explanation:

 \displaystyle 21^{2} = 21 \times 21 = 441, so \displaystyle 21 = \sqrt{441}

\displaystyle 441 > 425, so 

\displaystyle 21 = \sqrt{441} > \sqrt{425}

Example Question #1 : How To Find The Square Root

Which is the greater quantity?

(a) \displaystyle 6 \sqrt{ 7}

(b) \displaystyle 7 \sqrt{6}

Possible Answers:

(a) is greater

(a) and (b) are equal

(b) is greater

It is impossible to tell from the information given

Correct answer:

(b) is greater

Explanation:

(a) \displaystyle \left (6 \sqrt{7} \right )^{2} = 6^{2}\left ( \sqrt{7} \right ) ^{2} = 36 \cdot 7 = 252, so \displaystyle 6 \sqrt{7} = \sqrt{ 252 } 

(b) \displaystyle \left (7 \sqrt{6} \right )^{2} = 7^{2}\left ( \sqrt{6} \right ) ^{2} = 49 \cdot 6 = 294, so \displaystyle 7\sqrt{6} = \sqrt{ 294 }

\displaystyle 294 > 252,  

so 

\displaystyle \sqrt{294 }> \sqrt{252},

and 

\displaystyle 7\sqrt{6} > 6 \sqrt{7}

Example Question #2 : How To Find The Square Root

Column A     Column B       

\displaystyle \sqrt{100}         \displaystyle \sqrt{10.0}

 

Possible Answers:

The quantity in Column A is greater.

The quantity in Column B is greater.

There is no relationship between the quantities.

The quantities are equal.

Correct answer:

The quantity in Column A is greater.

Explanation:

The square root of 100 is 10, while the square root of 10 is between the square root of 9 and 16, so about 4. Therefore, Column A has to be greater.

Example Question #1 : Squares / Square Roots

Which of the following is equal to \displaystyle \sqrt{5^{2}+7^{2}+7} ?

Possible Answers:

\displaystyle 9

\displaystyle 11

\displaystyle 10

\displaystyle 8

None of the other responses is correct.

Correct answer:

\displaystyle 9

Explanation:

\displaystyle \sqrt{5^{2}+7^{2}+7}

\displaystyle =\sqrt{25 +49+7}

\displaystyle =\sqrt{81}

\displaystyle =9

Example Question #6 : How To Find The Square Root

Which of the following is equal to \displaystyle \sqrt{11^{2}+ 6 \cdot 8} ?

Possible Answers:

\displaystyle 14

\displaystyle 13

\displaystyle 12

None of the other responses is correct.

\displaystyle 15

Correct answer:

\displaystyle 13

Explanation:

\displaystyle \sqrt{11^{2}+ 6 \cdot 8}

\displaystyle = \sqrt{121+ 6 \cdot 8}

\displaystyle = \sqrt{121+ 48}

\displaystyle = \sqrt{169}

\displaystyle =13

Example Question #5 : How To Find The Square Root

Which of the following is equal to \displaystyle \sqrt{2^{3}+ 6^{2}+10^{2}} ?

Possible Answers:

\displaystyle 11

None of the other responses is correct.

\displaystyle 14

\displaystyle 13

\displaystyle 12

Correct answer:

\displaystyle 12

Explanation:

\displaystyle \sqrt{2^{3}+ 6^{2}+10^{2}}

\displaystyle =\sqrt{8+36 +100}

\displaystyle =\sqrt{ 144}

\displaystyle =12

Example Question #3 : How To Find The Square Root

\displaystyle V^{2} = 72\displaystyle V is positive.

Which is the greater quantity?

(a) \displaystyle V

(b) \displaystyle 8

Possible Answers:

It is impossible to tell which is greater from the information given

(B) is greater

(A) is greater

(A) and (B) are equal

Correct answer:

(A) is greater

Explanation:

Since \displaystyle Vis positive, we can compare \displaystyle V to 8 by comparing their squares. 

\displaystyle V^{2} = 72 and \displaystyle 8^{2} = 8 \times 8 = 64

\displaystyle V^{2} > 8^{2}, so \displaystyle V>8, making (A) greater.

Example Question #2 : Squares / Square Roots

\displaystyle F^{2}= 36

Which is the greater quantity?

(A) \displaystyle F

(B) \displaystyle 4

Possible Answers:

(A) and (B) are equal

(B) is greater

It is impossible to tell which is greater from the information given

(A) is greater

Correct answer:

It is impossible to tell which is greater from the information given

Explanation:

If \displaystyle F^{2} = 36, then one of two things is true - either \displaystyle F = 6 or \displaystyle F = -6.

However, \displaystyle 6 > 4 and \displaystyle -6< 4, so it is impossibe to tell whether (A) or (B) is greater.

Example Question #2 : Squares / Square Roots

\displaystyle Q^{2} = 49

Which is the greater quantity?

(A) \displaystyle Q

(B) \displaystyle -8

Possible Answers:

(A) and (B) are equal

(B) is greater

(A) is greater

It is impossible to tell which is greater from the information given

Correct answer:

(A) is greater

Explanation:

If \displaystyle Q^{2} = 49, then one of two things is true - either \displaystyle Q=7 or \displaystyle Q=- 7. Since \displaystyle 7 > -8 and \displaystyle -7 > -8\displaystyle Q > -8 either way, so (A) is greater.

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