Question

Find the sum of the first 40 positive integers divisible by 6.

Answer 1

The given numbers are the first 40 positive multiples of 6 

⇒ 6 × 1, 6 × 2, 6 × 3, ….., 6 × 40 

⇒ 6, 12, 18, ….. 240 

S_n = \(\frac{n}{2}\)(a + l) 

S₄₀ = \(\frac{40}{2}\)(6 + 240) 

= 20 × 246 

= 4920 

∴ S₄₀ = 4920