Question

the mean weight of a group of 5 boys is 50 kg then individual weight of four boys are 60 kg, 55 kg, 40 kg and 35 kg find the weight of the 50th boy

Answer 1

let the weight of 5th boy is x kg
$\frac{60 + 55 + 40 + 35 + x}{5} = 50 \\ \frac{190 + x}{5} = 50 \\ 190 + x = 250 \\ x = 250 - 190 \\x = 60$
the weight of 5th boy is 60 kg