Quantitative Aptitude - Arithmetic Ability Questions

The mean of marks secured by 50 students in division A of class X is 61, 25 students of division B is 57 and that of 50 students of division C is 55. What will be the mean of marks of the students of three divisions of Class X?

If a boat goes upstream at a speed of 21 km/h and comes back the same distance at 28 km/h. What is the average speed (in km/hr) for the total journey?

A mason can build a wall in 70 hours. After 7 hours he takes a break. What fraction of the wall is yet to be built?

Simple interest on a certain sum of money for 3 years at 8% per annum is half the compound interest on Rs. 16000 for 2 years at 10% per annum. The sum placed on simple interest is:

At 22% discount the selling price of a refrigerator is Rs 26000, what is the selling price if the discount is 40%?

If x2 + (1/x2) = 1, then what is the value of x48 + x42 + x36 + x30 + x24 + x18 + x12 + x6 + 1?

If x+y+z = 1, 1/x + 1/y + 1/z = 1 and xyz = -1, then x3+y3+z3 is equal to