Rachna borrowed a certain sum at the rate of 15% per annum. If she paid at the end of two years Rs. 1290 as interest compounded annually, find the sum she borrowed.
Given,
Rate = 15% p.a
Time = 2 years
C.I = Rs. 1290
Let principal = P
So,
Compound interest = 
= P
= 
= 
= 
Hence,
Principal = Rs. 4000
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