The ratio of present ages of Anil and Aakash is 4 : 5. Three years later their ages will be in ratio 7 : 8. What is the present age (in years) of Anil?
The average of 21 numbers is 12. The average of the first 11 numbers is 9 and the average of the last 11 numbers is 15. What is the value of the middle number?