A certain sum of money becomes triple of itself in 26 years at simple interest. In how many years it will becomes five times of itself?

52 years

Let Principal = 100 Rs

It becomes triple in 26 years = 300

So, Interest = 300-100=200

Same Principle become five times = 500

So, Interest = 500-100=400

So, Interest becomes double from 200 to 400

hence time also become double

i.e. 26×2=52 years

(it means if interest is double, time also double itself)