Quantitative Aptitude - Arithmetic Ability Questions

Painter 'A' can paint a house in 10 days and 'B' can do it in 20 days. With help of 'C', they did the job in 5 days only. Then, 'C' alone can do the job in:

A box contains 5 green, 4 yellow and 3 white marbles. Threemarbles are drawn at random. What is the probability thatthey are not of the same colour ?

If  x = a + 1/a, y = a - 1/a, then the value of x4+y4-2x2y2

Which number is 30% less than 80% of 800?

If a merchant offers a discount of 10% on the list price, then she makes a loss of 25%. What % profit or % loss will she make if she sells at a discount of 20% of the list price?

Amar can complete a work in 30 days and Raman can complete the same work in 15 days. If both of them work together, then in 4 days what percent of the total work will be completed?

In the given figure, MNOP is a square of side 6 cm. What is the value ( in cm ) of radius of circle?

Radius of base of a hollow cone is 8 cm and its height is 15 cm. A sphere of largest radius is put inside the cone. What is the ratio of radius of base of cone to the radius of sphere?