ISEE Upper Level Quantitative : Factors / Multiples

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

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Example Questions

Example Question #1 : How To Factor A Number

Which of the following is the prime factorization of 333?

Possible Answers:

333 cannot be factorized further

Correct answer:

Explanation:

To find the prime factorization, break the number down as a product of factors, then keep doing this until all of the factors are prime.

Example Question #2 : How To Factor A Number

Give the prime factorization of 91.

Possible Answers:

91 is a prime number.

Correct answer:

Explanation:

Both are prime factors so this is the prime factorization.

Example Question #3 : How To Factor A Number

How many factors does 40 have?

Possible Answers:

Correct answer:

Explanation:

40 has as its factors 1, 2, 4, 5, 8, 10, 20, and 40 - a total of eight factors.

Example Question #3 : How To Factor A Number

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

Possible Answers:

Correct answer:

Explanation:

27 has four factors: 

Their sum is .

Example Question #4 : How To Factor A Number

Add all of the factors of 30.

Possible Answers:

Correct answer:

Explanation:

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

.

Example Question #13 : Numbers And Operations

Which is the greater quantity?

(a) The number of factors of 169

(b) The number of factors of 121

Possible Answers:

It is impossible to tell from the information given

(a) and (b) are equal

(b) is greater

(a) is greater

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 #6 : How To Factor A Number

Which is the greater quantity?

(a) The number of factors of 15

(b) The number of factors of 17

Possible Answers:

(a) is greater.

It is impossible to tell from the information given.

(b) is greater.

(a) and (b) are equal.

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 : How To Factor A Number

Which is the greater quantity?

(a) The product of the integers between  and  inclusive

(b) The sum of the integers between  and  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:

Example Question #5 : How To Factor A Number

Which is the greater quantity?

(a) The sum of the factors of

(b) The sum of the factors of

Possible Answers:

(a) is greater.

(b) is greater.

It is impossible to tell from the information given.

(a) and (b) are equal.

Correct answer:

(b) is greater.

Explanation:

(a) The factors of  are  Their sum is 

.

(b) The factors of  are  Their sum is 

.

(b) is greater.

Example Question #11 : Factors / Multiples

Which is the greater quantity?

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

(b) 2,500

Possible Answers:

(a) is greater

(b) is greater

It is impossible to tell from the information given

(a) and (b) are equal

Correct answer:

(b) is greater

Explanation:

The sum of the integers from  to  is equal to . 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:

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