at what rate of interest will a sum of money treble itself in 10 years

Question

answer this question elaboratelly with all steps . it is from the chapter comparing quantities.

Answer 1

Assuming simple interest, with a starting amount (principal) of A, interest I after 10 years =10A(r/100)=Ar/10 where r is the percentage rate. After 10 years the total amount is A+I=A+Ar/10=3A, because after 10 years A has grown to 3A.

So we need to solve A+Ar/10=3A for r. We can divide through by A:

1+r/10=3, r/10=2, r=20%.