A stationery booth sells staplers in packs of 5 and 6. At first, there were 5 times as many packs of 5 as packs of 6. After selling half of the packs of 5 and some packs of 6, Mr Heng packs 9 additional packs of 6. How many packs of 5 are sold if there are 10 times as many packs of 5 as packs of 6 and there is a total of 560 unsold staplers?
| |
Packs of 5 |
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 |
|
+ 9 |
| After |
1x10 =
10 u |
|
Comparing the number
of packs in the end |
10 u |
1 u |
The number of packs of 5 in the end is repeated. Make the number of packs of 5 in the end the same. LCM of 1 and 10 is 10.
The number of packs of 5 at first is repeated. Make the number of packs of 5 at first the same. LCM of 20 and 5 is 20.
Number of staplers
left unsold |
Packs of 5
|
Packs of 6
|
Total
|
| Number |
10 u |
1 u |
|
| Value |
5 |
6 |
|
| Total value |
50 u |
6 u |
56 u |
Total number of staplers left unsold
= (10 u x 5) + (1 u x 6)
= 50 u + 6 u
= 56 u
56 u = 560
1 u = 560 ÷ 56 = 10
Number of packs of 6 sold
= (4 u - 1 u) + 9
= 3 u + 9
= 3 x 10 + 9
= 30 + 9
= 39
Answer(s): 39
