Question

The sum of first 20 terms of the sequence 0.7 , 0.77 , 0.777,............, is

Answer 1

HERE
a=0.7
d=0.77-0.7=0.07
n=20
S20=20/2(0.7+(20-1)0.07)
10(0.7+19*0.07)
10(0.7+1.33)
2.03*10
20.3