Question

The compound interest on a certain sum for 2 yrs is rs 40.80 and simple interest is rs 40.00. find the rate of interest per annum and the sum.

Answer 1

compound interest=40.80
time=2 yr.
Rate of interest=?
simple interest=40.00
now, compound interest-simple interest
40.80-40=.80
2×.80÷40×100
4% is the answer means rate of interest

Answer 2

40.80=p{ (1+r/100)^2 -1}
40.80=p(1+r^2/10000+2r/100-1)
40.80=pr(r/10000+2/100)
40=2pr/100
divide both
40.80/40=(r/10000+2/100)/2/100
4080/4000=(r+200)/10000×50
4080/4000×10000/50=r+200
202-200=r
r=2%
wrong calculation in the end in picture ...
please mark it as a brainliest answer