SI for 2 years=40
THUS,SI for 1 year=40/2=20
As for the first year CI and SI are always same so,
CI for first year=20
give that CI for 2 years is 41;
So CI for second year =41-20=21
Difference in CI for two successive years=21-20=1
1 is the interest for one year on the interest of first year,that is,on rupees 20;
therefore; the rate is 5% per annum.
Hope i helped!!