Question

the mean weight of 180 students in a school is 50 kg the mean weight of boys is 60 kg while that of girls is 45 kg find the number of boys and girls in the school

Answer 1

Let the no. of boys be x .

so No. of girls = (180-x).

A/Q,  60 x + (180-x) × 45 = 180×50

⇒ 60 x + 180×45 - 45 x = 180×50

⇒ 15 x = 180 (50-45)

⇒ 15 x = 900

∴ x = 60

no. of boys = 60

''     '' girls = 120

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Answer 2

Let the no. of boys be x .

so No. of girls = (180-x).

A/Q,  60 x + (180-x) × 45 = 180×50

⇒ 60 x + 180×45 - 45 x = 180×50

⇒ 15 x = 180 (50-45)

⇒ 15 x = 900

∴ x = 60

no. of boys = 60

''     '' girls = 120