What is the difference between compound interest and simple interest on Rs. 2500 for 2 years at 4% per annum?

The simple interest on a certain sum of the money at 4 % per annum for 4 years is Rs.80 more than the interest on the same sum for 3 years at 5 % per annum. Find the sum.

The ratio of present ages of Ratna and Shantanu is 5:4. After 19 years, the ratio of their ages will be 10:9. What is Ratna's present age?

The top of two poles of height 24m and 36 m are connected by a wire. If the wire makes an angle of 60° with the horizontal, then the length of the wire is 

A contractor undertakes to finish a certain work in 124 days and employed 120 men. After 64 days, he found that he had already done 2/3 of the work. How many men can be discharged so that the work may finish in time ?

The number of sides in two regular polygons are in the ratio of 5 : 4. The difference between their Interior angles of the polygon is 6⁰ . Then the number of sides are 

A seller gives 15% discount on an item, if he marked up the price of item 40% above C.P and while selling he cheats the buyer by giving 10% less in weight. Find this overall profit percent (approximately).

What is the average of the first five prime numbers?