A stationery booth sells markers in packs of 4 and 7. At first, there were 3 times as many packs of 4 as packs of 7. After selling half of the packs of 4 and some packs of 7, Mr Ng packs 13 additional packs of 7. How many packs of 4 are sold if there are 6 times as many packs of 4 as packs of 7 and there is a total of 62 unsold markers?
| |
Packs of 4 |
Packs of 7 |
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 markers
left unsold |
Packs of 4
|
Packs of 7
|
Total
|
| Number |
6 u |
1 u |
|
| Value |
4 |
7 |
|
| Total value |
24 u |
7 u |
31 u |
Total number of markers left unsold
= (6 u x 4) + (1 u x 7)
= 24 u + 7 u
= 31 u
31 u = 62
1 u = 62 ÷ 31 = 2
Number of packs of 7 sold
= (4 u - 1 u) + 13
= 3 u + 13
= 3 x 2 + 13
= 6 + 13
= 19
Answer(s): 19
