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The average weight of 150 students in a certain classis 60 kg. The mean weight of the boys from theclass is 70 kg, while that of the girl is 55 kg. Whatis the number of girls in the class?(1) 105(3) 95(2) 100(4) 60 |
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Answer» first of all the total numeber of student is 150certain class 60 kg boys weight 70 kg girl is 55 kgfind girls in class lets starttotal number of student - girl in 55 kg150 -5595 ans is 95 Total students in class = 150mean weight = 60 kgtotal weight = 150×60 = 9000 kg Let the total number of boys = xmean weight of boys = 70kgtotal weight of boys = 70×x = 70x kg total number of girls = total students - no. of boys =150 - xmean weight of girls= 55kgtotal 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 = 750/15⇒ x = 50 So number of boys = 50number of girls = 150 - 50 = 100 |
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