All ISEE Upper Level Quantitative Resources
Example Questions
Example Question #33 : How To Find Out If A Number Is Prime
and are prime numbers.
Which is the greater quantity?
(A)
(B) 175
(B) is greater
It is impossible to determine which is greater from the information given
(A) and (B) are equal
(A) is greater
(A) is greater
97 is the only prime number between 90 and 100, so . The only two primes between 80 and 90 are 83 and 89, so or . Therefore, either of the following holds:
or
(A) must be the greater quantity regardless.
Example Question #35 : How To Find Out If A Number Is Prime
and are prime numbers.
Which is the greater quantity?
(A)
(B) 80
(B) is greater
(A) and (B) are equal
(A) is greater
It is impossible to determine which is greater from the information given
It is impossible to determine which is greater from the information given
We show that it cannot be determined whether is greater than, less than, or equal to 80 by choosing two pairs of primes within the given ranges and adding.
Case 1:
.
Case 2:
In each case, , with and prime.
Example Question #91 : Factors / Multiples
, and and are positive integers.
is a prime number; is not a prime number.
Which is the greater quantity?
(a)
(b)
(b) is the greater quantity
(a) is the greater quantity
(a) and (b) are equal
It cannot be determined which of (a) and (b) is greater
It cannot be determined which of (a) and (b) is greater
, and and are positive integers, so each of and is an integer from 1 to 11 inclusive.
is a prime number, meaning that it can be equal to 2, 3, 5, 7, or 11. Testing each case:
, which is not prime.
, which is not prime.
, which is prime - we throw this case out.
, which is prime - we throw this case out.
, which is not prime.
In the first two cases, ; in the last case, . It cannot be determined which is the greater.
Example Question #42 : How To Find Out If A Number Is Prime
; and are positive integers.
is a prime number. is not.
Which is the greater quantity?
(a) 5
(b)
(a) and (b) are equal
It cannot be determined which of (a) and (b) is greater
(a) is the greater quantity
(b) is the greater quantity
(b) is the greater quantity
, and and are positive integers.
Therefore, must be an integer from 1 to 9, as must .
Since is prime, it can be any of 2, 3, 5, or 7.
Therefore, one of the following must hold:
Only in the first case is not a prime number (8 has four factors - 1, 2, 4, 8), so and .
Example Question #1 : Least Common Multiple
What is the least common multiple of 15 and 25?
is the lowest number that is a multiple of both 15 and 25, so we see which is the first number that appears in both lists of multiples.
The multiples of 15:
The multiples of 25:
Example Question #1 : Least Common Multiple
Which is the greater quantity?
(a)
(b)
(a) is greater.
(a) and (b) are equal.
Not enough information is given to answer the question.
(b) is greater.
Not enough information is given to answer the question.
We show that the given information is not enough by taking two cases:
and
and divide into , so and .
is prime and , so
.
Therefore, if , (b) is greater, and if , (a) is greater.
Example Question #1 : How To Find The Least Common Multiple
Which is the greater quantity?
(a)
(b)
(a) and (b) are equal.
It is impossible to tell from the information given.
(a) is greater.
(b) is greater.
(a) and (b) are equal.
The prime factorizations of 50 and 60 are:
The greatest common factor of 50 and 60 is the product of the prime factors they share:
The least common multiple of 50 and 60 is the product of all of the prime factors, with shared factors counted once:
,
(a) and (b) are equal.
Note: it is also a property of the integers that the product of the GCF and the LCM of two integers is equal to the product of the two integers themselves.
Example Question #452 : Isee Upper Level (Grades 9 12) Quantitative Reasoning
Which is the greater quantity?
(a)
(b)
(a) and (b) are equal
It is impossible to tell from the information given
(a) is greater
(b) is greater
(a) is greater
(a)
(b) To find , list their factors:
To find ,examine their prime factorizations:
(a) is greater.
Example Question #2 : Least Common Multiple
Which of the following is the greater quantity?
(A) The least common multiple of 25 and 30
(B) 300
(B) is greater
(A) and (B) are equal
It is impossible to determine which is greater from the information given
(A) is greater
(B) is greater
To find we can list some multiples of both numbers and discover the least number in both lists:
, so (B) is greater
Example Question #3 : Least Common Multiple
Which of the following is the least common multiple of 25 and 40?
List the first few multiples of both 25 and 40:
The least number in both lists of factors is 200.