Question

1. Find the sum of the following APs:
(i) 2,7,12, ..., to 10 terms.​

Answer 1

S10=245

Step-by-step explanation:

a=2, d= 7-2=5, n=10

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

n/2 (2a+ (n-1) d)S10=10/2 (2(2)+ (10-1) 5)

=5(4+9×5)

=5(4+45)

=5×49

S10=245