A stationery kiosk sells staplers in packs of 3 and 5. At first, there were 5 times as many packs of 3 as packs of 5. After selling half of the packs of 3 and some packs of 5, Mr Oh packs 11 additional packs of 5. How many packs of 3 and 5 are sold if there are 10 times as many packs of 3 as packs of 5 and there is a total of 70 unsold staplers?

	Packs of 3	Packs of 5
Comparing the number of packs at first	5x4 = 20 u	1x4 = 4 u
Before	2x10 = 20 u
Change 1	- 1x10 = - 10 u	- ?
Change 2		+ 11
After	1x10 = 10 u
Comparing the number of packs in the end	10 u	1 u

The number of packs of 3 in the end is repeated. Make the number of packs of 3 in the end the same. LCM of 1 and 10 is 10.

The number of packs of 3 at first is repeated. Make the number of packs of 3 at first the same. LCM of 20 and 5 is 20.

Number of staplers left unsold	Packs of 3	Packs of 5	Total
Number	10 u	1 u
Value	3	5
Total value	30 u	5 u	35 u

Total number of staplers left unsold
= (10 u x 3) + (1 u x 5)
= 30 u + 5 u
= 35 u

35 u = 70

1 u = 70 ÷ 35 = 2

Number of packs of 3 and 5  sold
= 10 u + (4 u - 1 u) + 11
= 10 u + 3 u + 11
= 13 u + 11
= 13 x 2 + 11
= 26 + 11
= 37

Answer(s): 37