Class B, C and D were given some sweets to sell for their donation drive. The average number of sweets the 3 classes had at first was 241. After Class C sold four times as many sweets as Class B and Class D sold ⁷₈ as many sweets as Class C, the average number of sweets the 3 classes had left was 54. How many sweets did Class B and Class D sell altogether?

Class B	Class C	Class D
1x2	4x2
	8x1	7x1
2 u	8 u	7 u

Class B : Class C : Class D
2 : 8 : 7

Total number of sweets that the 3 classes had at first
= 3 x 241
= 723

Number of sweets that the 3 classes left
= 3 x 54 
= 162

Number of sweets that were sold by 3 classes
= 723 - 162
= 561

2 u + 8 u + 7 u = 561
17 u = 561

1 u = 561 ÷ 17 = 33

Total number of sweets sold by Class B and Class D
= 2 u + 7 u
= 9 u
= 9 x 33
= 297

Answer(s): 297