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 ₹ 400 amounts to ₹ 480 in 4 years. What will it amount to if the rate of interest is increased by 2 %? 

Out of ₹ 20, 000 Narendra gives some amount on loan at simple interest rate 8 % per annum and rest amount at simple interest rate 4 / 3 % per annum. At the end of year he earns ₹ 800. The amount given at 8 % rate will be – 

A sum of money was lent at simple interest at certain rate for 3 years. Had it been lent at 2.5 % per annum higher rate, it would have fetched ₹ 540 more. The money lent was 

At what simple rate of interest a sum is double in 8 years?