Quantitative Aptitude - Arithmetic Ability Questions

a and b are irrational numbers such that a+b = q is a rational number; then a­b is

The average marks of 40 students in an examination was 25. It was later found that the marks of one student had been wrongly entered as 73 instead of 37. What is the value of correct average?

If a is positive and a2+1a2 = 7, then a3 + 1a3 = ?

What is the value of (32 cos6x – 48 cos4x + 18 cos2x – 1)/[4 sin x cos x sin (60 – x) cos (60 – x) sin (60 + x) cos (60 + x)]?

If a + b = 5 and ab = 6, then what is the value of a3 + b3?

The value of x13+x-13x23-1+x-23

In the question, two equations I and II are given. You have to solve both the equations and give answer

$$\begin{gathered} x2-11x+28=0 \\ y2-18y+81=0 \end{gathered}$$

At a telephone exchange, three phones ring at intervals of 20 sec, 24 sec and 30 seconds. If they ring together at 11 : 25 a.m, when will they next ring together?