Class S, T and U were given some sweets to sell for their donation drive. The average number of sweets the 3 classes had at first was 229. After Class T sold four times as many sweets as Class S and Class U sold ²₃ as many sweets as Class T, the average number of sweets the 3 classes had left was 45. How many sweets did Class S and Class U sell altogether?

Class S	Class T	Class U
1x3	4x3
	3x4	2x4
3 u	12 u	8 u

Class S : Class T : Class U
3 : 12 : 8

Total number of sweets that the 3 classes had at first
= 3 x 229
= 687

Number of sweets that the 3 classes left
= 3 x 45 
= 135

Number of sweets that were sold by 3 classes
= 687 - 135
= 552

3 u + 12 u + 8 u = 552
23 u = 552

1 u = 552 ÷ 23 = 24

Total number of sweets sold by Class S and Class U
= 3 u + 8 u
= 11 u
= 11 x 24
= 264

Answer(s): 264