Question

The mean marks of 150 students in a class is 65.6. The mean marks of boys is 60 and mean marks of girls is 72. Find the number of boys and girls.
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Answer 1

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Answer 2

Total students in class =150

mean weight=60kg

total weight =150×60=9000kg

Let the total number of boys =x

mean weight of boys =70kg

total weight of boys =70×x=70xkg

total number of girls = total students - no. of boys =150−x

mean weight of girls=55kg

total weight of girls =55×(150−x)=55×150−55x=(8250−55x)kg

Total weight = weight of boys + weight of girls

9000=70x+(8250−55x)

9000=70x+8250−55x

9000−8250=70x−55x

750=15x

x=

15

750

x=50

So number of boys =50

number of girls =150−50=100

this one is correct by the way