Factors, multiples, primes, HCF and LCM

Question 1 of 10

Which of these numbers is a prime number?

Question 2 of 10

A number ending in 0 is divisible by both 2 and 5.

Question 3 of 10

Every multiple of 6 is also a multiple of 3.

Question 4 of 10

Bells ring at intervals of 20 minutes and 45 minutes. They ring together at 8:00 a.m. (a) Find the LCM of 20 and 45. (b) At what time will they next ring together? Show your working.

Question 5 of 10

Bells ring at intervals of 15 minutes and 10 minutes. They ring together at 8:00 a.m. (a) Find the LCM of 15 and 10. (b) At what time will they next ring together? Show your working.

Question 6 of 10

Find the LCM of 40 and 64.

Question 7 of 10

Find the HCF of 8 and 14.

Question 8 of 10

The prime factorisation of 12 is 2 × 2 × 3.

Question 9 of 10

How many prime numbers are there between 1 and 20?

Question 10 of 10

Find the LCM of 81 and 72.