Question

15,10,5..... In this AP sum of first 10 terms is.....?

The answer is -75
Please solve with proper steps.

Answer 1

Hey friend

Here is your answer

15,10,5..........

a=15

d=10-15= -5

n=10

$sn = \frac{n}{2} \times (2a + (n - 1)d) \\ \\ sn = \frac{10}{2} \times (2 \times 15 + (10 - 1) \times - 5) \\ \\ sn = 5 \times (30 + (9) \times - 5) \\ \\ sn = 5 \times (30 - 45) \\ \\ sn = 5 \times ( - 15) \\ \\ sn = - 75$

So the sum of first 10 terms of this AP are -75

HOPE THIS HELPS YOU ☺

Answer 2

Sum of first 10 terms is - 75