The ratio of number of girls to number of boy is 2 : 3. If the average weight of the boys is 60 kg and the average weight of both is 51kg, then the average weight of girls is:
Answer & explanation
Correct answer: option 3
Given =
The ratio of number of girls to number of boys is 2 : 3
Average weight of the boys is = 60 kg
The average weight of both is = 51kg
Let the average weight of girls is = x
Total average = \(\frac{Total \; weight \; of \; the \; boys + Total \; weight \; of \; girls}{The \; total \; number \; of \; girls \; and \; boys}\)
51 = \(\frac{(60 × 2) + (x × 3)}{2 + 3}\)
51 = \(\frac{(120) + (3x)}{5}\)
255 - 120 = 3x
x = \(\frac{135}{3}\)
x = 45kg