Class S, T and U were given some chocolate bars to sell for their donation drive. The average number of chocolate bars the 3 classes had at first was 210. After Class T sold twice as many chocolate bars as Class S and Class U sold ⁵₆ as many chocolate bars as Class T, the average number of chocolate bars the 3 classes had left was 56. How many chocolate bars did Class S and Class U sell altogether?

Class S	Class T	Class U
1x3	2x3
	6x1	5x1
3 u	6 u	5 u

Class S : Class T : Class U
3 : 6 : 5

Total number of chocolate bars that the 3 classes had at first
= 3 x 210
= 630

Number of chocolate bars that the 3 classes left
= 3 x 56 
= 168

Number of chocolate bars that were sold by 3 classes
= 630 - 168
= 462

3 u + 6 u + 5 u = 462
14 u = 462

1 u = 462 ÷ 14 = 33

Total number of chocolate bars sold by Class S and Class U
= 3 u + 5 u
= 8 u
= 8 x 33
= 264

Answer(s): 264