ISEE Upper Level Math : Prime Numbers

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

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Example Questions

Example Question #11 : Prime Numbers

Which of the following is a prime number?

Possible Answers:

\(\displaystyle 51\)

\(\displaystyle 13\)

\(\displaystyle 39\)

\(\displaystyle 81\)

Correct answer:

\(\displaystyle 13\)

Explanation:

Which of the following is a prime number?

The answer here is 13, because 13 has no factors other than 1 and itself.

51 is divisible by 3 and 17.

39 is divisible by 13 and 3.

81 is divisible by 9, 3, and 27

Example Question #32 : Numbers And Operations

Find the sum of all the prime numbers between \(\displaystyle 50\) and \(\displaystyle 70\).

Possible Answers:

\(\displaystyle 309\)

\(\displaystyle 181\)

\(\displaystyle 187\)

\(\displaystyle 240\)

\(\displaystyle 238\)

Correct answer:

\(\displaystyle 240\)

Explanation:

The prime numbers between \(\displaystyle 50\) and \(\displaystyle 70\) are \(\displaystyle 53\), \(\displaystyle 59\), \(\displaystyle 61\), and \(\displaystyle 67\). Their sum is:

\(\displaystyle 53 + 59 + 61 + 67 = 240\).

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