P works thrice as fast as Q, whereas P and Q together can work four times as fast as R. If P, Q, and R together work on a job, in what ratio should they share the earnings?

If 2 boys and 2 girls are to be arranged in a row so that the girls are not next to each other, how many possible arrangements are there?

The age of Mr. X last year was the square of a number and it would be the cube of a number next year. What is the least number of years he must wait for his age to become the cube of a number again?

The outer surface of a 4 cm × 4 cm × 4 cm cube is painted completely in red. It is sliced parallel to the faces to yield sixty-four 1 cm × 1 cm × 1 cm small cubes. How many small cubes do not have painted faces?

There is a milk sample with 50% water in it. If $\frac{1}{3}$rd of this milk is added to an equal amount of pure milk, then water in the new mixture will fall down to:

There are thirteen 2-digit consecutive odd numbers. If 39 is the mean of the first five such numbers, then what is the mean of all the thirteen numbers?