Question

Write 78 as a product of prime factors

Answer 1

78 = 2 ⋅ 3 ⋅ 13

Explanation:

78 ends with an even digit, so is divisible by 2 and we find: 78 = 2 ⋅ 39

39 ends with an odd digit, so is not divisible by 2 .

The digits of 39 add up to a multiple of 3 , namely 3 + 9 = 12 . So we can tell that 39 is divisible by 3 : 39 = 3 ⋅ 13

13 is a prime number, not divisible by any number greater than 1 or less than 13 .

So the prime factorization of

78 is:

78= 2 ⋅ 3 ⋅ 13

Answer 2

13 is a prime number, not divisible by any number greater than 1 or less than 13. So the prime factorisation of 78 is: 78 = 2 ⋅ 3 ⋅ 13 This can also be represented by a factor tree:

Explanation: