2022 · Q64
Consider the following table in respect of students of 4 schools who appeared in a test : School Number of students Average marks in the test I 60 60 II 50 80 III 50 40 IV X 50 If the average marks of the students of all four schools are 58, then how many students appeared from School - IV?
Elementary MathematicsStatistics
- A38
- B40
- C42
- D44
Explanation
(60×60+50×80+50×40+50X)/(160+X) = 58 gives 9600+50X = 9280+58X, so X = 40. This is a weighted mean: total marks 9600+50X over 160+X students equals 58. The keyed option is B.