mean score

Question

50 children took a test. 5 children got 100%, another 10 got 90%, and yet the average class score was 45%. What is the mean score for the children below the 70th percentile?

a. 24.3% b. 25.7% c. 23.4% d. 25.0%

Answer 1

first off note that the 70th percentile refers to the remaining 35 students. 

 

Total score by ALL students = 50*45= 2250

First 5 students score = 5*100 = 500

Next 10 students score = 10*90 = 900

 

Therefore the total for the remaining 35 = 2250-900-500 = 850

The average = 850/35 = 170/7 = 24.3 approx