Madhya Pradesh Police Exam Model Paper 4

Given:
Average of weight of 4 students = 70
Formula used:
Average = Sum of all observation/Number of observation
Calculation:
Sum of the weight of 4 students $=70\times 4=280$
Sum of the weight of 3 students $=60\times 3=180$
Weight of student who left the group $=280\mathit{–}180=100\mathit{k}\mathit{g}$
Formula used:
Quantity removed = [Change in number of quantities × Original average] - [Change in average × Final number of quantities]
$=\left[1\times 70\mathit{–}\left(-10\right)\times 3\right]$
$\Rightarrow 100\mathit{k}\mathit{g}$