The average of 80 numbers is 105. The average of the first 21 numbers ...
The average of the last two numbers

Hence, Option A is correct.
View all questions of this testThe average of 80 numbers is 105. The average of the first 21 numbers ...
Given Data:
- Total numbers: 80
- Average of all 80 numbers: 105
- Average of first 21 numbers: 104
- Average of next 57 numbers: 103
Solution:
Finding the sum of all 80 numbers:
- Sum of all 80 numbers = Average of all 80 numbers * Total numbers
- Sum of all 80 numbers = 105 * 80
- Sum of all 80 numbers = 8400
Finding the sum of the first 21 numbers:
- Sum of the first 21 numbers = Average of the first 21 numbers * 21
- Sum of the first 21 numbers = 104 * 21
- Sum of the first 21 numbers = 2184
Finding the sum of the next 57 numbers:
- Sum of the next 57 numbers = Sum of all 80 numbers - Sum of the first 21 numbers
- Sum of the next 57 numbers = 8400 - 2184
- Sum of the next 57 numbers = 6216
Finding the sum of the last 2 numbers:
- Sum of the last 2 numbers = Sum of the next 57 numbers - Sum of the first 21 numbers
- Sum of the last 2 numbers = 6216 - 2184
- Sum of the last 2 numbers = 4032
Finding the average of the last 2 numbers:
- Average of the last 2 numbers = Sum of the last 2 numbers / 2
- Average of the last 2 numbers = 4032 / 2
- Average of the last 2 numbers = 2016
Therefore, the average of the last two numbers is 2016/2 = 172.50.
So, option (a) 172.50 is the correct answer.