ACT Preparation / Unit 15 ACT 1408 short lesson, about 20 seconds
Weighted Average
Captions available
The idea
A weighted average multiplies each value by its weight, adds the products, and divides by the total weight. Groups of different sizes need it.
In practice
20 students averaging 80 and 30 averaging 90: (1,600 + 2,700)/50 = 86, not 85.
Where people slip
Averaging the two averages ignores group size; it works only when the groups are equal.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
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