If the same number be added to the numbers 5, 11, 15 and 31, the resulting numbers are in proportion. Find the number.

The present age of a man is twice that of his son. Eight years hence, their ages will be in the ratio 7 : 4. Find their present ages.

The sum of three odd numbers is 87. The largest of these is:

1. 27

2. 31

3. 29

4. 25