Quantitative Aptitude - Arithmetic Ability Questions

The average marks obtained in a class of 50 students is 70%. The average of first 25 is 60% and that of 24 is 80%. What is the marks obtained by the last student?

Let A(O,-1), B(0,3) and C(2,1) be three points. Let   △1 be the area of the triangle ABC and △2 be the area of the triangle formed by the mid points of the sides of the triangle whose vertices are A, B and C such that △1=1 ,△2=x Find the value of x .

A car travelling at an average speed of 72 km/hr takes 9 minutes to travel a certain distance. By how much should it increase its speed (in km/hr) to travel the same distance in 8 minutes?

Nine years later, age of B will be equal to the present age of A. Sum of A's age 3 years later and B's age 4 years ago is 76. If C is half of the present age of B, then what will be C's age (in years) after 10 years?

If 1/2 is added to a number and the sum is multipled by 3, the result is 21. Then the number is

If cot A = n/(n + 1) and cot B = 1/(2n + 1), then what is the value of cot (A + B)?

Find 150% of X, if X is the least number which when divided by 6, 7, 8, 9 and 12 leaves remainders 2, 3, 4, 5 and 8 respectively.

A bookseller bought 500 text books for  20,000. He wanted to sell them at a profit so that he get 50 books free. At what profit percent should he sell them?