Question

The 16th term of an AP is 5 times its third term.If the 10th term is 41,then find the sum of its first fifteen terms.

Answer 1

therefore the sum of its first fifteen terms of ap is 495

Answer 2

Answer:

A16=5a3

a10 =41

s15,=?

a16=5(a+2d)

5a+10d

.a+9d=41......1. ( Multiply by 4)

4a+36d=164 .....2

a+15d=5a+10d=4a-5d......3

Sustract 3-2

d=4

a +36 =41

a=5

S15=n/2(20-14×4)

15/2×66

495

Step-by-step explanation: