A stationery kiosk sells notebooks in packs of 3 and 6. At first, there were 5 times as many packs of 3 as packs of 6. After selling half of the packs of 3 and some packs of 6, Mr Yee packs 20 additional packs of 6. How many packs of 3 are sold if there are 10 times as many packs of 3 as packs of 6 and there is a total of 216 unsold notebooks?
|
Packs of 3 |
Packs of 6 |
Comparing the number of packs at first |
5x4 = 20 u |
1x4 = 4 u |
Before |
2x10 = 20 u |
|
Change 1 |
- 1x10 = - 10 u |
- ? |
Change 2 |
|
+ 20 |
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 notebooks left unsold |
Packs of 3
|
Packs of 6
|
Total
|
Number |
10 u |
1 u |
|
Value |
3 |
6 |
|
Total value |
30 u |
6 u |
36 u |
Total number of notebooks left unsold
= (10 u x 3) + (1 u x 6)
= 30 u + 6 u
= 36 u
36 u = 216
1 u = 216 ÷ 36 = 6
Number of packs of 6 sold
= (4 u - 1 u) + 20
= 3 u + 20
= 3 x 6 + 20
= 18 + 20
= 38
Answer(s): 38