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?
Answer & explanation
Correct answer: option 3
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