Quantitative Aptitude - Arithmetic Ability Questions

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

If a - b = 1 and ab = 6, then what is the value of a3- b3?

If x = 6+26, then what is the value of x-1 + 1x-1 ?

A thief is stopped by a policeman from a distance of 400 metres. When the policeman starts the chase, the thief also starts running. Assuming the speed of the thief as 5 km/h and that of policeman as 9 km/h, how far the thief would have run, before he is over -taken by the policeman?

Krishna cycled a distance of 90 km at a certain speed. If he cycled 3 km slower every hour, he would have taken 5 more hours to reach his destination. What is the speed in kmph at which Krishna actually cycled?

A can do as much work in 4 days as B can do in 5, and B can do as much work in 6 days as C in 7. In what time will C do a piece of work which A can do in a week ?

Manoj can do a piece of work in 42 hours. If he is joined by Jayashree who is 100% more efficient, in what time they will finish the work together?

A train moves at the speed of 40 m/s and crosses a bridge of length 550 metres in 25 seconds. What is the length (in metres) of the train?