Question

The mean Mark's of 50 students in a class is 27. if the mean Mark's of boys is 25 and that of girls is 30.
Find the number of boys
CLASS -X Chapter:Statistics ;NCERT CBSE​

Answer 1

Answer:

30

Step-by-step explanation:

Mean = sum/product *of observations

Here,

Mean mark of all students(boys+girls) is:

=> 27 = (sum of marks of boys+girls)/50

=> 1350 = sum of marks of boys + girls

Let boys be x and then girls = 50 - x

=> mean of boys = 25

=> (sum of marks)/x = 25

=> sum of marks = 25x

Similarly, sum of marks of girls is 30(50-x)

From above,

=> sum of marks of boys + girls = 1350

=> 25x + 30(50 - x) = 1350

=> 25x + 1500 - 30x = 1350

=> 1500 - 1350 = 30x - 25x

=> 150 = 5x

=> 30 = x, which means,

There are 30 boys and (50-30=20) girls