If I save $50 at in accrues interest with an APR of 4%, how long until l have $125?

Question

does anyone know the formula for this question as well as the solved answer?

Answer 1

Accrued Amount = Principal*(1+i)ⁿ ; A = P(1+i)ⁿ; given that i is the annual compounded interest rate

 

A/P = (1+i)ⁿ

 

125/50 = (1.04)ⁿ

 

you can take logs on both sides:

 

log₁₀ 2.5 = n*log₁₀ 1.04

 

0.3979 = n*0.01703

 

therefore n = 0.3979/0.01703 = 23.36 years