Question

In an A.P., if the first term (a) = −16 and the common difference (d) = −2, then the sum of first 10 terms is ______.

पर्याय

• −200

• −70

• −250

• 250

Answer 1

In an A.P., if the first term (a) = −16 and the common difference (d) = −2, then the sum of first 10 terms is −250.

Explanation:

Given,

1st term = a = −16

common difference = d = −2

then, we know that

the sum of n terms = S_n

`s_n = n/2[2a + (n - 1)d`

Here n = 10

So, `s_10 = 10/2[2 xx (-16) + (10 - 1)*(-2)`

= 5 [−32 −18]

= 5 [−50]

= −250