A number whose prime factorisation is 3 × 5 × 11 is:
165
33
55
15
3 × 5 × 11 = 165
The square root of a number whose prime factorisation is
2 x 2 x 3 x 3 x 3 x 3 x 5 x 5 is:
Question 11
Write five pairs of prime numbers less than 20 whose sum is divisible by 5. [Hint: 3 + 7 = 10]