Question

find the sum of the AP 2, 7, 12 upto 20 terms​

Answer 1

a=2

d = 7-2 = 5

n= 20

sum of the AP

$\frac{20}{2} (2 \times 2 + 19 \times 5)$

= 10 ( 4 + 95 )

= 10 × 99

= 990