Question

The first term of an arithmetic progression is 7 and eleventh term is 32 . The sum all the terms in the progression is 2790 . Find the number of terms in the progression

Answer 1

Step-by-step explanation:

a=7

11th term=32

a+10d=32

7+10d=32

10d=25

d=25/10

d=2.5

Sn=2790

$sn = n \div 2 \times a + n - 1 \times d$

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

2790=n/2(7+(n-1)2.5)

simplify it

then you will set an quadratic equation

do that equation by factorisation