Question

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

Answer 1

If 2³ × 3^a × b × 7 is the prime factorisation of 2520, then 5a + 2b = 20.

Explanation:

From the prime factorisation 2520 = 2³ × 3² × 5 × 7, we match a = 2 and b = 5. 

This gives 5a + 2b = 5 × 2 + 2 × 5 

= 10 + 10

= 20