A man invested Rs.25000 on simple interest at R% p.a. If interest received by man is three twentieth of the principal after three years, then find ‘R’?

The difference of simple interest from two banks on ₹8,000 in 3 years is ₹800. If the rate of interest per annum in two banks are R1 and R2, then what is the value of R1 - R2? (Where R1 > R2)

The principal which gives ₹ 1 interest per day at a rate of 5 % simple interest per annum is 

A person invested some amount at the rate of 12 % simple interest and a certain amount at the rate of 10 % simple interest for 1 year. He received yearly interest of Rs. ₹ 130, but if he had interchanged the amount invested, he would have received 4 more as interest. How much did he invest at 12 % simple interest? 

If the simple interest on a certain sum of money for 2 years in one fifth of the Principal, then find rate of interest per annum. 

What equal installment of annual payment will discharge a debt which is due as ₹ 848 at the end of 4 years at 4 % per annum simple interest? 

In what time will the annual simple interest rate at , 72 rupees becomes 81 rupees?

A sum of money lent out at simple interest amounts to ₹720 after 2 years and 1020 after a further period of 5 years. Find the principal.