Question

1. If the first and last terms of an AP are 10 and 15 respectively. What will be the num-
ber of terms in it, if their sum is 125 ?​

Answer 1

Answer:

10

Step-by-step explanation:

sum of n terms = n/2 * (a + l) where a is the first term and l is the last term of the AP.

it is given that their sum is 125 and the first and last terms are 10 and 15 respectively.

=>125= n/2 * (10+ 15)

=>250= 25n

=>n = 10

so, the AP has 10 terms