a) the mean weight of 150 students in a certain class is 60 kg. The mean weight of boys is 70 kg and that of girls in the class is 55 kg. Find the numbet of boys and girls in the class.
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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
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