Question

Find the sum of first 20 terms of the arithmetic progression 3, 8,13..using the formula​

Answer 1

Step-by-step explanation:

Here, a = 3 d= 5 n = 20

Then,

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

S 20 = 10 × ( 6 + 95 )

S 20 = 1010