Answer by
SammyChua (9)

Here's an example:
Suppose the weight of the first quiz is 70 and the weight of the second quiz is 30. You got 80 on the first quiz and 70 on the second quiz. To get the weighted average,
(70*80 + 30*70)/(70+30)
= (5600+2100)/(100)
= 7700 / 100
= 77
Therefore, the weighted average in the example is 77.