Quantitative Aptitude - Arithmetic Ability Questions

The average marks of 18 students in an examination was 60. It was later found that the marks of one student had been wrongly entered as 63 instead of 36. The correct average is:

A can do a certain job in 12 days. B is 60% more efficient than A. Then B can do the same piece of work in

X can complete 5/7 part of a work in 10 days and Y can complete 3/4 part of the same work in 9 days. In how many days will both complete 13/21 part  of the total work?

If a number is decreased by 10%, it becomes 54. To make it 72, it should be increased by

If 27% of an electricity bill is deducted, Rs 1825 is still to be paid. How much was the bill?

A's income is Rs 140 more than B's income and C's income is Rs 80 more than D's. If the ratio of A's and C's income is 2:3 and the ratio of B's and D's income is 1:2, then the incomes of A, B, C and D are respectively

Two motorcycles are moving towards each other with the speeds of 38 km/hr and 88 km/hr respectively. One second before the collision what will be the distance (in metres) between the two motorcycles?

cos3A is equal to