Question

13
A principal amount at 5% yearly interest rate after 3 yesars earned Rs. 1200
as simple interest, should the rate of interest and duration remain the same
how much will the compound interest be on the principal ?
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Answer 1

let p be principal

$si = \frac{p \times 3 \times 5}{100}$

$1200 = \frac{p \times 3 \times 5}{100}$

$p = 8000$

$therefore \: the \: principal \: is \: rs.8000$

$a = p \: 1 + \frac{ {r}^{3} }{ {100} }$

$= a = 8000 \binom{ {21}^{3} }{20}$

$a = 8000(1.1576)$

$ci = a - p$

$ci \: = rs.1260$

hope it helps you