Practice!

Sample Problem

Linda, Alex and Lucy have an average of 84 videos. Linda and Alex have an average of 93 videos. Alex and Lucy have an average of 75 videos. What is the average number of videos Linda and Lucy have?

  videos

Solution

The three girls have a total of 84 × 3 = 252 videos.

Linda and Alex have a total of 93 × 2 = 186 videos.

Alex and Lucy have a total of 75 × 2 = 150 videos.

Therefore, Alex has 150 + 186 – 252 = 84 videos.

Linda has 186 – 84 = 102 videos.

Lucy has 150 – 84 = 66 videos.

Therefore, Linda and Carry have an average of (102 + 66) ÷ 2 = 168 ÷ 2 = 84 videos.