The difference between compound interest and the simple interest on some amount of money lend at a rate of 7% p. a. for 3 years is Rs. 800. What is the approx. principal amount?
Let the money lent be Rs. X
Now,
Compound Interest = P (1 + R/100)n - P
And,
SI = (P × r × n)/100
Where, P = Principal Amount
r = Rate of interest (per annum)
n = Number of years
Hence,
X × [1 + 7/100]3 - X - (X × 7 × 3)/100 = 800
X × (1.07)3 - 1.21X = 800
X = 53181