The average of the three numbers is 15. The average of the second and third number is 12.5. What is the first number?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is Option 4 i.e. 20.
We know that,
Average = Sum of observations/Number of observations
Now,
The sum of three number = 15 × 3 = 45
The sum of the second number and third number = 12.5 × 2 = 25
First number = 45 - 25 = 20
Hence, the first number is 20