Prime numbers

Question 1

Which statement correctly tells whether 51 is a prime or composite number and why?

Accepted Answer

51 is a composite number because it can be divided evenly by 3.

Answer

51 is a composite number because it is an odd number.

Answer

51 is a prime number because its only factors are 1 and 51.

Answer

51 is a prime number because it is not divisible by 5.

Question 2

Liam has 91 stickers and wants to arrange them into equal piles with no stickers left over. To decide if 91 can be split into piles other than one pile or 91 piles, he needs to know if it is prime or composite. Which statement correctly tells whether 91 is prime or composite and why?

Accepted Answer

91 is composite because it can be written as 7 × 13.

Answer

91 is prime because none of the square numbers less than 91 multiply together to make 91.

Answer

91 is prime because it is not divisible by 2, 3, or 5.

Answer

91 is composite because the sum of its digits (9 + 1 = 10) is not a prime number.

Question 3

Mr. Patel has 59 stickers and wants to split them into equal piles without any leftovers. Which explanation correctly shows why 59 is a prime number?

Accepted Answer

59 can be divided only by 1 and 59, so it has exactly two factors, which means it is prime.

Answer

59 can be divided by 1, 59, and also by 13, so it has three factors, making it composite.

Answer

59 is prime because it is odd and greater than 2.

Answer

59 has factors 1, 59, and 59 × 1, which means it has more than two factors, so it is not prime.

Try three questions

Which statement correctly tells whether 51 is a prime or composite number and why?

Liam has 91 stickers and wants to arrange them into equal piles with no stickers left over. To decide if 91 can be split into piles other than one pile or 91 piles, he needs to know if it is prime or composite. Which statement correctly tells whether 91 is prime or composite and why?

Mr. Patel has 59 stickers and wants to split them into equal piles without any leftovers. Which explanation correctly shows why 59 is a prime number?

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