If certain sum, at simple interest turns into thrice of actual amount in 4 years. Find out time to become the amount thirteen times of initial amount? 

An amount doubles itself in 5 years with simple interest. What is the rate of interest per year?

A person lends 40 % of his sum of money at 15 % per annum, 50 % of rest at 10 % per annum and the rest at 18 % per annum rate of interest. What would be the annual rate of interest, if the interest is calculated on the whole sum? 

A sum of ₹ 1750 is divided into two parts such that the interests on the first part at 8 % simple interest per annum and that on the other part at 6 % simple interest per annum are equal. The interest on each part (in rupees) is 

The simple interest for four years is one fourth of the principal. At the same rate, which amount become Rs.450 total amount in 2 years?

A sum of ₹ 7, 930 is divided into 3 parts and given at loan at 5 % simple interest to A, B and C for 2, 3 and 4 years respectively. If the amounts of all three are equal after their respective periods of loan, then the A received a loan of 

What is the ratio of the simple interest earned on a certain amount at the rate of 21% per annum for 8 years to that earned on the same sum at the same rate for 21 years?