The average of 4 numbers is 24. The average of the first 2 numbers is double the average of the last 2 numbers. What is the sum of the last 2 numbers?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is Option 4 i.e. 32.
Let the numbers be a, b, c, and d
We know that,
Average = Sum of observations/Number of Observations
Now,
⇒ 24 = (a + b + c + d)/4
⇒ 96 = (a + b + c + d).....(1)
The average of the first two numbers is double the average of the last two numbers:
⇒ (a + b)/2 = 2 × (c + d)/2
⇒ (a + b) = 2(c + d)
⇒ a + b = 2c + 2d
Putting in eq 1
⇒ 96 = 2c + 2d + c + d
⇒ 96 = 3c + 3d
⇒ c + d = 32
Thus, The sum of the last two numbers is 32