Question

IB exams

If a sum of money at simple interest doubles in 6 years, it will become 4 times in ?

Answer 1

Let sum of money = P
it doubled in 6 years
A = 2P
T = 6 yrs
I = A - P = 2P - P = P

I = PTR
⇒ P = P×6×R 
⇒ R = 1/6

TO become 4 times,
A = 4P
I = 4P - P = 3P
T = ?

I = PTR
⇒3P = P×T×(1/6)
⇒ T = 6×3 = 18yrs