give solution

Question

A certain investment takes 18 years to grow 5 times.How long would it take to double itself?what annual rate of simple interest does the investment earn .

Answer 1

Let the principle be 100.

Then amount will be 500.

Interest= 400

Time = 18 yrs

R=?

I=PRT/100

400=100*R*18/100

400*100/100*18=R

400/18=R

 

22.22 % = R

NOW SUM SHOULD BE DOUBLED MEANS 200

MEANS INTREST ON 100 IS 100.

I=PRT/100

100=100*400/18*T/100

100=400 T / 18

 

100 * 18  / 400 = T

 

4.5 = T