Question

If 2³ × 3^a × b × 7 is the prime factorisation of 2520, then 5a + 2b = _________ .

Answer 1

Prime factorisation of 2520 is

2520 = 2³ × 3² × 5¹ × 7¹

Therefore, a = 2 and b = 5

5a + 2b = 5(2) + 2(5)
= 10 + 10
= 20

Hence, 5a + 2b = 20.