Question

What is the sum of first 10 terms of the A. P. 15,10.5.......​

Answer 1

Answer:

a = 15

d = -5

Sn = n/2(2a + (n-1)(d))

sum of first 10 term

S10 = 10/2(2(15) + 9(-5))

S10 = 5 (30 - 45)

S10 = 5(-15)

S10 = -75

hope this will help you