Question

the mean marks obtained by a class of 40 students is 65. the mean marks of half of the students is found to be 45. the mean marks of the remaining students is (a) 85 (b) 60 (c) 70 (d) 65

Answer 1

Given mean marks of 40 students is 65
Let x be the sum of their marks
x /40=65
Therefore, x = 2600
Now , mean marks of half of the students is 45
That is...
x'/20= 45
x' = 900
That means the sum of marks of half of the students is 900
Therefore , sum of marks of remaining students is 2600-900= 1700
Therefore, the mean marks of remaining students is
1700/20
Which is equal to 85
Option A is correct