In a stall, some mini-helicopters and rubber duckies were on sale. ¹₁₁ of the items were mini-helicopters. ²₃ of the mini-helicopters and 1356 rubber duckies were sold. There were ¹₁₂ of the items left in the stall. How many mini-helicopters and rubber duckies were there in the stall at first?

	Mini-helicopters	Rubber duckies	Total
Comparing mini-helicopters  and rubber duckies at first	1x12 = 12 u	10x12 = 120 u	11x12 = 132 u
Before	3x4 =  12 u		12x11 = 132 u
Change	- 2x4 = - 8 u	- 1356	- 11x11 = - 121 u
After	1x4 = 4 u	7 u	1x11 = 11 u

 
The total number of toys at first is repeated.  Make the total number of toys at first the same. LCM of 11 and 12 is 132.

The number of mini-helicopters at first is repeated.  Make the number of mini-helicopters the same. LCM of 12 and 3 is 12. 

Number of rubber duckies left
= 11 u - 4 u
= 7 u

Number of rubber duckies sold
= 120 u - 7 u
= 113 u

113 u = 1356

1 u = 1356 ÷ 113 = 12

Number of mini-helicopters and rubber duckies at first
= 132 u
= 132 x 12
= 1584

Answer(s): 1584