A bookstore sells markers in packs of 5 and 8. At first, there were 10 times as many packs of 5 as packs of 8. After selling half of the packs of 5 and some packs of 8, Mr Gan packs 11 additional packs of 8. How many packs of 5 are sold if there are 10 times as many packs of 5 as packs of 8 and there is a total of 290 unsold markers?
| |
Packs of 5 |
Packs of 8 |
Comparing the number
of packs at first |
10x2 =
20 u |
1x2 =
2 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 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 10 is 20.
Number of markers
left unsold |
Packs of 5
|
Packs of 8
|
Total
|
| Number |
10 u |
1 u |
|
| Value |
5 |
8 |
|
| Total value |
50 u |
8 u |
58 u |
Total number of markers left unsold
= (10 u x 5) + (1 u x 8)
= 50 u + 8 u
= 58 u
58 u = 290
1 u = 290 ÷ 58 = 5
Number of packs of 8 sold
= (2 u - 1 u) + 11
= 1 u + 11
= 1 x 5 + 11
= 5 + 11
= 16
Answer(s): 16
