A stationery kiosk sells notebooks in packs of 4 and 7. At first, there were 4 times as many packs of 4 as packs of 7. After selling half of the packs of 4 and some packs of 7, Mr Cheong packs 17 additional packs of 7. How many packs of 4 are sold if there are 8 times as many packs of 4 as packs of 7 and there is a total of 351 unsold notebooks?
|
Packs of 4 |
Packs of 7 |
Comparing the number of packs at first |
4x4 = 16 u |
1x4 = 4 u |
Before |
2x8 = 16 u |
|
Change 1 |
- 1x8 = - 8 u |
- ? |
Change 2 |
|
+ 17 |
After |
1x8 = 8 u |
|
Comparing the number of packs in the end |
8 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 8 is 8.
The number of packs of 4 at first is repeated. Make the number of packs of 4 at first the same. LCM of 16 and 4 is 16.
Number of notebooks left unsold |
Packs of 4
|
Packs of 7
|
Total
|
Number |
8 u |
1 u |
|
Value |
4 |
7 |
|
Total value |
32 u |
7 u |
39 u |
Total number of notebooks left unsold
= (8 u x 4) + (1 u x 7)
= 32 u + 7 u
= 39 u
39 u = 351
1 u = 351 ÷ 39 = 9
Number of packs of 7 sold
= (4 u - 1 u) + 17
= 3 u + 17
= 3 x 9 + 17
= 27 + 17
= 44
Answer(s): 44