Question

A sum doubles itself in 16 years, then in how many years will it triple itself; rate of interest being simple.​

Answer 1

Formula for simple interest I is given as

I =PRT where P is the principal investment, r the interest rate in % (usually in decimal ) and T the duration of investment.

So the Final Investment Value A is given as

A = P+PRT)

A =P (1+RT).

So if investment P doubles in 16 years, then

2P =P (1+16R) from where

R = 1/16. This is the agreed interest for this investment.

For investment P to become 3P,

3P =P (1+1/16T)

3=1+1/16T

2=1/16T

T =32years.