Question

find the sum of 20 terms of the a.p 3,6,9,12.....​

Answer 1

Answer:

630

Step-by-step explanation:

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

here n=20

d=3

a=3

substitute in the formula.....

Answer 2

Answer:

a=3 , d=3 , n=20 , t20 = ?

tn= a+ (n-1)d

T20= 3+ (20-1)*3

= 3+57

=60

T20 = 60