Question

- The principal, at a certain rate of interest, doubles in 5 years by the
simple interest. In how many years, the same principal with the same
rate of interest becomes five times?
(1) 10 years (2) 12 integer one by two years (3) 20 years
(4) 25 years
1​

Answer 1

Answer:

see here ans. 20 years

I use this formula:...

given year/given year = (n-1)times/(n-1)times

whereas n=how many times (according to the que.)

we use formula

so,

5year =double means 2

5 year =2

x = 5

we assume yrs as x

formula

5-1/x-1=2-1/5-1

x=20 years