A bookshop sells markers in packs of 2 and 5. At first, there were 8 times as many packs of 2 as packs of 5. After selling half of the packs of 2 and some packs of 5, Mr Seah packs 20 additional packs of 5. How many packs of 2 and 5 are sold if there are 8 times as many packs of 2 as packs of 5 and there is a total of 126 unsold markers?
|
Packs of 2 |
Packs of 5 |
Comparing the number of packs at first |
8x2 = 16 u |
1x2 = 2 u |
Before |
2x8 = 16 u |
|
Change 1 |
- 1x8 = - 8 u |
- ? |
Change 2 |
|
+ 20 |
After |
1x8 = 8 u |
|
Comparing the number of packs in the end |
8 u |
1 u |
The number of packs of 2 in the end is repeated. Make the number of packs of 2 in the end the same. LCM of 1 and 8 is 8.
The number of packs of 2 at first is repeated. Make the number of packs of 2 at first the same. LCM of 16 and 8 is 16.
Number of markers left unsold |
Packs of 2
|
Packs of 5
|
Total
|
Number |
8 u |
1 u |
|
Value |
2 |
5 |
|
Total value |
16 u |
5 u |
21 u |
Total number of markers left unsold
= (8 u x 2) + (1 u x 5)
= 16 u + 5 u
= 21 u
21 u = 126
1 u = 126 ÷ 21 = 6
Number of packs of 2 and 5 sold
= 8 u + (2 u - 1 u) + 20
= 8 u + 1 u + 20
= 9 u + 20
= 9 x 6 + 20
= 54 + 20
= 74
Answer(s): 74