at what rate percent per annum will sum of money double in 20 years ?
"explanation : hint : if sum of money becomes ( z times ) in ( t ) years at simple interest , then rate of interest ( r ) can be calculated using the formula : rate of interest ( r ) % = 100 ( z – 1 ) / t here , principal amount is not given . hence , we can directly use the trick to calculate the rate of interest . rate of interest ( r ) % = 100 ( 2 – 1 ) / 20 rate of interest ( r ) % = 5 % p . a . answer is d"
divide(const_100, 20)