In how many least number of complete years a sum of money become more than four times of itself at the rate of 50 percent per annum on simple interest?

7 years

Let principal = 1R

Here, If principal becomes 4 times, then

Amount = 4R

S.I. = 4R - 1R = 3R

Total Rate of Interest = \(\frac{3R}{1R}\) × 100 = 300%

Formula:

Total Rate of Interest = Rate p.a. × Time

Hence,

300% = 50% × Time

Time = \(\frac{300}{50}\) = 6 years

The sum of money becomes 4 times in 6 years. Therefore, the sum becomes more than 4 times in 7 years.