Question

find the sum of 50 terms of the sequence 7,7.7,7.77,7.777,........
..

Answer 1

an=a+(n-1)d this formula can help u for solve it

Answer 2

a=7 d=0.7 n=50
sn=n/2 [2a+(n-1)d]
=50/2 [2×7+(50-1)×0.7]
=25 (14+34.3)
=127.5

hence sum of 50 terms is 127.5