Find the sum of the following AP:2, 7, 12,…, to 10 terms.

1.	Find the sum of the following AP:2, 7, 12,…, to 10 terms.
Answer» Given A.P: 2, 7, 12, …… to 10 terms a = 2; d = a₂ – a₁ = 7 – 2 = 5; n = 10 S_n = \(\frac{n}{2}\) [2a + (n – 1)d] ∴ S₁₀ = \(\frac{10}{2}\) [2 × 2 + (10 – 1)5] = 5 [4 + 9 × 5] = 5 [4 + 45] = 5 × 49 = 245

Answer»

Given A.P: 2, 7, 12, …… to 10 terms

a = 2; d = a₂ – a₁ = 7 – 2 = 5; n = 10

S_n = \(\frac{n}{2}\) [2a + (n – 1)d]

∴ S₁₀ = \(\frac{10}{2}\) [2 × 2 + (10 – 1)5]

= 5 [4 + 9 × 5]

= 5 [4 + 45]

= 5 × 49

= 245

Discussion