An amount of money becomes Tk. 1,860 at an interest rate of 8% in 3 years. How many years the money would take to become Tk. 2040 at the same interest rate?

at 8% rate, interest of 100 tk in 3 years= 3X8=24 principal+interest=124 tk when  principal+interest is 124 then capital 100 taka when  principal+interest is 1860 then capital 100 x 1860/124 taka=1500 tk

so interest=(1860-1500)tk=360 tk 360 tk interest in 3 years 1      tk    interest in 3/360 years

540 tk interest = 3X 540/360=4.5 year