Quantitative Aptitude - Arithmetic Ability Questions

What is the average of first 30 multiples of 9?

An 80 litre mixture of water and acid contains 20% acid. How much acid should be added to make the acid 60% in the new mixture?

The percentage change of a number when it is first decreased by 10% and then increased by 10% is

A car travels a certain distance at 34 km/h and comes back at 66 km/h. What is the average speed for total journey?

If x -­ y = ­7 and x + y = 13, then x2 - y2 is

Find the value of 777777?

The value of the expression 2(sin6θ+cos6θ) - 3(sin4θ+cos4θ) + 1 is

ax + 3y = 6 has slope -2/3. What is the value of a?