The average of four numbers is 20. If the average of the first two numbers is 15, then what is the average of the last two numbers?

22 18 25 20

25

Sum of 4 numbers = 4 × 20 = 80 Sum of first 2 numbers = 2 × 15 = 30 Sum of last 2 numbers = 80 - 30 = 50 Average of last 2 numbers = \(\frac{50}{2}\)  = 25