Question

A certain sum of money triples itself in 5 years at simple interest. In how many years it will be five times?

Answer 1

let the Principal be Rs.100
amount=300

SI=p*r*t/100
200=100*r*5/100
200=5r
200/5=r
40=r

the rate of interest is 40%

required amount=500
required interest=400

400=100*40*t/100
400=40t
400/40=t
10=t

it will take 10 years to be 5 times.

Answer 2

Let rate be r, principle amount be p and the number of years bet
After 5 years,
⇒ Simple Interest = 3p – p = 2p
⇒ 2p = (p × r × 5)/100
⇒ r = 40
After t years,
⇒ Simple Interest = 5p – p = 4p
⇒ 4p = (p × 40 × t)/100
⇒ t = 10
∴ It will take 10 years