Question
A sum doubles in 20 years at simple interest. What is
the rate of interest?Solution
Let the original amount = ₹100
Then after 20 years, it becomes ₹200
So, interest = ₹100
SI = (P × R × T)/100
100 = (100 × R × 20)/100
100 = 20R/100
R = 100/20 = 5
Rate = 5% per year
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