Question

Find the sum of the following AP
2,7,12.... To 10 terms.​

Answer 1

S = 5 [ 2×2 + 9×5 ]

= 5 [ 4 +45 ]

= 5 × 49

= 245

ANSWER

Answer 2

Given AP: 2, 7,12........ to 10 terms

Total number of terms, n = 10

First Term in series, a = 2

Common difference, d = 12 - 7 = 7 - 3 = 5

We know,

$\boxed{{S}_{n} = \dfrac{n}{2}[2a + (n-1)d]}$

${S}_{10} = \dfrac{10}{2}[2(2) + (10 - 1)5] \\ = 5[4+45] \\ = 245$

${S}_{10} = 245$

So, the sum of the given AP is 245