If the difference between CI and SI for 3 years at the rate of 10% is Rs 31. Find the principle.

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

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 –