For an A.P, first term a = 5 and common difference d = 3. The sum of first 8 terms is ___

Open in App

Solution

Sum of first n terms, s
$= \frac{n}{2} [2 a + (n - 1) d]$
$= \frac{8}{2}$ $(2 \times 5 + (8 - 1) \times 3)$
$= 4 (10 + 21)$
$= 31 \times 4$
= 124

Suggest Corrections

Similar questions

For an A.P, first term a = 5 and Common difference d = 3. Find the sum of first 8 terms.___

The sum of the first n terms of an AP whose first term is 8 and the common difference is 20 is equal to the sum of the first 2n terms of another AP, whose first term is - 30 and the common difference is 8. find n?

Q. Question 33
The sum of the first n terms of an AP whose first term is 8 and the common difference is 20 is equal to the sum of first 2n terms of another AP whose first term is –30 and the common difference is 8. Find n.

Q. The sum of the first

n

terms of an

A P

whose first term is

8

and the common difference is

20

is equal to the sum of first

2 n

terms of another

A P

whose first term is

40

and the common difference is

6

. Find

n

Q. The sum of the first ten terms of an AP is equal to

155

and the sum of the first two terms of a GP is

9

. How many values for the first term of an AP is possible if the first term of an AP is equal to the common ratio of a GP and the first term of a GP is equal to to the common difference of a AP

Join BYJU'S Learning Program

For an A.P, first term a = 5 and common difference d = 3. The sum of first 8 terms is ___

Sum of first n terms, s =n2[2a+(n−1)d] =82(2×5+(8−1)×3) =4(10+21) =31×4 = 124

Sum of first n terms, s
$= \frac{n}{2} [2 a + (n - 1) d]$
$= \frac{8}{2}$ $(2 \times 5 + (8 - 1) \times 3)$
$= 4 (10 + 21)$
$= 31 \times 4$
= 124