Algebra> A man saves Rs. 200 in each of the first ...

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

sudhanshu , 11 Years ago

Grade 12

2 Answers

SHAIK AASIF AHAMED

Last Activity: 10 Years ago

Hello student,

So after 21 months his total saving be Rs.11040

Thanks and Regards

Shaik Aasif

askIITians faculty

Rishi Sharma

Last Activity: 4 Years ago

Dear Student,
Please find below the solution to your problem.

Savings are:
200,200,200,240,280,.......uptonterms
But 200,240,280,......(n−2) terms forms an A.P
Since, sum of n terms of an AP =Sn=2n[2a+(n−1)d], where first term is a and common difference d
∴ According to question
400+2n−2[2(200)+(n−2−1)40]=11040 ......Sum =11040
⇒400+(n−2)[200+(n−3)20]=11040

⇒(n−2)[200+20n−60]=10640
⇒(n−2)(20n+140)=10640
⇒20(n+7)(n−2)=10640
⇒n2+5n−14=532
⇒n2+5n−546=0
⇒(n+26)(n−21)=0
⇒n=21
So, total time =21 months.

Thanks and Regards