Question

adhithi required Rs2500 after 12 weeks to send her daughter.She saved Rs 100

Answer 1

AP = 100+120+140+An

N = 12

A = 100

D = 20

An = A+(N-1)D

= 100+(12-1)20

= 100+220 = 320

The required An = 320

Then , Sn = N÷2{2A+(N-1)D}

= 12÷2 {2×100+(12-1)20}

= 6×450 = 2520

So , she will be able to send her daughter to school after 12 weeks .