ISEE Upper Level Quantitative : ISEE Upper Level (grades 9-12) Quantitative Reasoning

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

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Example Questions

Example Question #1 : How To Factor A Number

What is the sum of all of the factors of 27?

Possible Answers:

\(\displaystyle 12\)

\(\displaystyle 39\)

\(\displaystyle 40\)

\(\displaystyle 13\)

\(\displaystyle 36\)

Correct answer:

\(\displaystyle 40\)

Explanation:

27 has four factors: \(\displaystyle 1, 3, 9, 27.\)

Their sum is \(\displaystyle 1 + 3 + 9 + 27 = 40\).

Example Question #1 : Other Factors / Multiples

Add all of the factors of 30.

Possible Answers:

\(\displaystyle 41\)

\(\displaystyle 42\)

\(\displaystyle 55\)

\(\displaystyle 71\)

\(\displaystyle 72\)

Correct answer:

\(\displaystyle 72\)

Explanation:

The factors of 30 are 1, 2, 3, 5, 6, 10, 15, and 30. Their sum is

\(\displaystyle 1+2+3+5+ 6+10+15 + 30 = 72\).

Example Question #7 : Other Factors / Multiples

Which is the greater quantity?

(a) The number of factors of 169

(b) The number of factors of 121

Possible Answers:

(a) is greater

(b) is greater

It is impossible to tell from the information given

(a) and (b) are equal

Correct answer:

(a) and (b) are equal

Explanation:

Each number has only three factors. 121 has 1, 11, and 121 as factors; 169 has 1, 13, and 169 as factors. The answer is that the quantities are equal.

Example Question #8 : Other Factors / Multiples

Which is the greater quantity?

(a) The number of factors of 15

(b) The number of factors of 17

Possible Answers:

(b) is greater.

(a) and (b) are equal.

(a) is greater.

It is impossible to tell from the information given.

Correct answer:

(a) is greater.

Explanation:

(a) 15 has four factors, 1, 3, 5, and 15.

(b) 17, as a prime, has two factors, 1 and 17.

Therefore, (a) is greater.

Example Question #9 : Other Factors / Multiples

Which is the greater quantity?

(a) The product of the integers between \(\displaystyle -1,000,000\) and \(\displaystyle 1,000,000\) inclusive

(b) The sum of the integers between \(\displaystyle -1,000,000\) and \(\displaystyle 1,000,000\) inclusive

Possible Answers:

(b) is greater.

It is impossible to tell from the information given.

(a) and (b) are equal.

(a) is greater.

Correct answer:

(a) and (b) are equal.

Explanation:

The quanitites are equal, as both can be demonstrated to be equal to .

(a) One of the integers in the given range is , so one of the factors will be , making the product .

(b) The sum of the numbers will be:

\(\displaystyle 0 + (-1 + 1) + (-2 + 2) + (-3 + 3) + ... + (-1,000,000+ 1,000,000)\)

\(\displaystyle 0 + 0 + 0+...+0 = 0\)

Example Question #16 : Factors / Multiples

Which is the greater quantity?

(a) The sum of the factors of \(\displaystyle 18\)

(b) The sum of the factors of \(\displaystyle 20\)

Possible Answers:

It is impossible to tell from the information given.

(b) is greater.

(a) is greater.

(a) and (b) are equal.

Correct answer:

(b) is greater.

Explanation:

(a) The factors of \(\displaystyle 18\) are \(\displaystyle 1, 2, 3, 6, 9, 18.\) Their sum is 

\(\displaystyle 1+ 2+3+ 6+ 9+18 = 39\).

(b) The factors of \(\displaystyle 20\) are \(\displaystyle 1, 2, 4, 5, 10, 20.\) Their sum is 

\(\displaystyle 1+ 2+4+5+10+20 = 42\).

(b) is greater.

Example Question #17 : Numbers And Operations

Which is the greater quantity?

(a) The sum of all of the two-digit even numbers 

(b) 2,500

Possible Answers:

(b) is greater

It is impossible to tell from the information given

(a) and (b) are equal

(a) is greater

Correct answer:

(b) is greater

Explanation:

The sum of the integers from \(\displaystyle m\) to \(\displaystyle n\) is equal to \(\displaystyle \frac{\left ( n+m \right )\left ( n-m+1 \right )}{2}\). We take advantage of the fact that the sum of the even numbers from 10 to 98 is equal to twice the sum of the integers from 5 to 49, as seen here:

\(\displaystyle 10+12 + 14+...+98\)

\(\displaystyle =2 \left ( 5+ 6+7+...+49\right )\)

\(\displaystyle =2\cdot \frac{\left ( 49+5 \right )\left ( 49-5+1 \right )}{2}\)

\(\displaystyle =54 \times 45 = 2,430 < 2,500\)

Example Question #11 : Other Factors / Multiples

What is the prime factorization of \(\displaystyle 16ab^2\)?

Possible Answers:

\(\displaystyle 2\cdot 2\cdot 2\cdot 2\cdot 2\cdot a\cdot b\cdot b\)

\(\displaystyle 2\cdot 2\cdot 2\cdot a\cdot b\cdot b\)

\(\displaystyle 2\cdot 2\cdot 2\cdot 2\cdot a\cdot b\)

\(\displaystyle 2\cdot 2\cdot 2\cdot 2\)

\(\displaystyle 2\cdot 2\cdot 2\cdot 2\cdot a\cdot b\cdot b\)

Correct answer:

\(\displaystyle 2\cdot 2\cdot 2\cdot 2\cdot a\cdot b\cdot b\)

Explanation:

First make a factor tree for 16. Keep breaking it down until you get all prime numbers (for example: \(\displaystyle 4\times 4\), which then yields \(\displaystyle 2\times 2\times 2\times 2\)). Then, at the end, remember to factor the variables as well. Since the b term is squared, that means there are two of them. Therefore, the final answer is \(\displaystyle 2\cdot 2\cdot 2\cdot 2\cdot a\cdot b\cdot b\).

Example Question #12 : Other Factors / Multiples

Which one is greater?

 

\(\displaystyle (a)\) number of factors of \(\displaystyle 100\)

\(\displaystyle (b)\ 10\)

Possible Answers:

\(\displaystyle (a)\) and \(\displaystyle (b)\) are equal

 

it is not possible to tell based on the information given.

\(\displaystyle (b)\) is greater

\(\displaystyle (a)\) is greater

Correct answer:

\(\displaystyle (b)\) is greater

Explanation:

Factors of \(\displaystyle 100\) are:

 

\(\displaystyle 1,2,4,5,10,20,25,50\ and\ 100\). So it has \(\displaystyle 9\) factors which is less than \(\displaystyle 10\).

 

Example Question #13 : Other Factors / Multiples

Which one is greater?

 

\(\displaystyle (a)\) The sum of all of the factors of \(\displaystyle 72\)

\(\displaystyle (b)\ 200\)

 

Possible Answers:

\(\displaystyle (a)\) and \(\displaystyle (b)\) are equal

\(\displaystyle (a)\) is greater

\(\displaystyle (b)\) is greater

it is not possible to tell based on the information given.

Correct answer:

\(\displaystyle (b)\) is greater

Explanation:

Factors of \(\displaystyle 72\) are:

 

\(\displaystyle 1,2,3,4,6,8,9,12,18,24,36\ and\ 72\). So we can write:

 

\(\displaystyle 1+2+3+4+6+8+9+12+18+24+36+72=195\)

 

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