Question

In an A.P. a = 2 and d = 3, then find S₁₂

Answer 1

a = 2 and d = 3   ......[Given]

Since S_n = `"n"/2 [2"a" + ("n" - 1)"d"]`,

S₁₂ = `12/2 [2(2) + (12 - 1)(3)]`

= 6[4 + 11(3)]

= 6(4 + 33)

= 6(37)

= 222