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
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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
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