A stationery kiosk sells pencils in packs of 4 and 6. At first, there were 3 times as many packs of 4 as packs of 6. After selling half of the packs of 4 and some packs of 6, Mr Peh packs 13 additional packs of 6. How many packs of 4 and 6 are sold if there are 6 times as many packs of 4 as packs of 6 and there is a total of 270 unsold pencils?

	Packs of 4	Packs of 6
Comparing the number of packs at first	3x4 = 12 u	1x4 = 4 u
Before	2x6 = 12 u
Change 1	- 1x6 = - 6 u	- ?
Change 2		+ 13
After	1x6 = 6 u
Comparing the number of packs in the end	6 u	1 u

The number of packs of 4 in the end is repeated. Make the number of packs of 4 in the end the same. LCM of 1 and 6 is 6.

The number of packs of 4 at first is repeated. Make the number of packs of 4 at first the same. LCM of 12 and 3 is 12.

Number of pencils left unsold	Packs of 4	Packs of 6	Total
Number	6 u	1 u
Value	4	6
Total value	24 u	6 u	30 u

Total number of pencils left unsold
= (6 u x 4) + (1 u x 6)
= 24 u + 6 u
= 30 u

30 u = 270

1 u = 270 ÷ 30 = 9

Number of packs of 4 and 6  sold
= 6 u + (4 u - 1 u) + 13
= 6 u + 3 u + 13
= 9 u + 13
= 9 x 9 + 13
= 81 + 13
= 94

Answer(s): 94