Class L, M and N were given some sweets to sell for their fund-raising project. The average number of sweets the 3 classes had at first was 212. After Class M sold twice as many sweets as Class L and Class N sold ⁶₇ as many sweets as Class M, the average number of sweets the 3 classes had left was 58. How many sweets did Class L and Class N sell altogether?

Class L	Class M	Class N
1x7	2x7
	7x2	6x2
7 u	14 u	12 u

Class L : Class M : Class N
7 : 14 : 12

Total number of sweets that the 3 classes had at first
= 3 x 212
= 636

Number of sweets that the 3 classes left
= 3 x 58 
= 174

Number of sweets that were sold by 3 classes
= 636 - 174
= 462

7 u + 14 u + 12 u = 462
33 u = 462

1 u = 462 ÷ 33 = 14

Total number of sweets sold by Class L and Class N
= 7 u + 12 u
= 19 u
= 19 x 14
= 266

Answer(s): 266