In a shop, the number of cartons of pear juice sold was
12 the number of cartons left. When 90 more cartons were sold, the total number of cartons sold was 9 less than
67 the number of cartons the shop had at first. How many cartons were there at first?
|
Sold |
Left |
Total |
Before |
1x7 = 7 u |
2x7 = 14 u |
3x7 = 21 u
|
Change |
+ 90 |
- 90 |
|
After |
7 u + 90 |
14 u - 90 |
21 u |
Comparing the total number of cartons sold and the total number of cartons at first |
6x3 - 9 = 18 u - 9 |
|
7x3 = 21 u |
The total number of cartons is repeated. Make the total number of cartons the same. LCM of 3 and 7 is 21.
The number of cartons sold in the end is repeated.
18 u - 9 = 7 u + 90
18 u - 7 u = 90 + 9
11 u = 99
1 u = 99 ÷ 11 = 9
Number of cartons at first
= 21 u
= 21 x 9
= 189
Answer(s): 189