Question

The average weight of $40$ students in a class is $75$ kg. By mistake the weights of two students are read as $74$ kg and $66$ kg respectively instead of $66$ kg and $54$ kg. Find the corrected average weight of the class

Answer 1

The average weight of $40$ students is $75kg$

$\therefore$ Total weight of $40$ students $=40\times 75=3000kg$

$\Rightarrow$ Correct total weight of $40$ students $=3000-74-66+66+54=2980$

$\Rightarrow$ Required correct average weight $=\frac{2980}{40}=74.5$