At what rate percent will a sum of money double itself in 6 years ?
Let principal =P
Rate of interest =R%
Given: Amount =2P
Since, Amount = Principal + Simple Interest
⇒2P=P+S.I.⇒S.I.=2P-P⇒S.I.=P
We know that
Simple interest =P×R×T100
Then,
P=P×R×6100 ⇒R=100×P6×P⇒R=1006⇒R=16.66%
Hence, the required interest rate is 16.66%.