Question

On a certain​ exam, Tony corrected 20 papers and found the mean for his group to be 70. Alice corrected the remaining 10 papers and found that the mean for her group was 90. What is the mean of the combined group of 30 ​students?

Answer 1

The mean of the combined group is 76.67 ≈ 77

Explanation:

1. The sum of the grades in Tom's group is 20×70 = 1400
2. The sum of grades in Alice's group is 10×90=900
3. The sum of gradees in the combined group is =1400+900=2300
4. Then the mean grade of the combined group is
   `(2300)/(30)=76.67`

where

• 2300 is the sum of the all grades in the combined group
• 30 is the total number of people in the group