Question

A man saves Rs. 200 in each of the first three months of his service. In each of the subsequent months his saving increases by Rs. 40 more than the saving of immediately previous month. His total saving from the start of service will be Rs. 11040 after ?
A) 19 months
B) 21 months
C) 18 months
D) 20 months

Answer 1

Total savings = 200 + 200 + 200 + 240 + 280 + ... to n months = 11040
= 120 + 80 + 160 + 40 + 200 + 240 + ....n terms
= 40 + 80 + 120 + 160 + 200 + 240 + ...n terms
= n/2[2a + (n-1)d] + 80 + 40 = 11040
= n/2[240 + (n-1)40] = 10920
= n[6+n-1] = 546
= n[n+5] = 546
n = 21

Thx for giving me a chance

Answer 2

Answer:

21 is the answer........