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Question
primary 5 | Maths
| Whole Numbers
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At first, blue pen = 5 units
Red pen = 1 unit
Total = 6 units
After, red pen = 2 units
blue pen = 1 unit
Total = 3 units
Since total number of pens is the same, we make the number of units the same.
3 units x 2 = 6 units
So in the end,
Blue pen = 1 units x 2 = 2 units
Red pen = 2 unit x 2 = 4 units
So you can see that number of blue pens decreased by 3 units. Number of red pens increased by 3 units
3 units = 21 pens
1 unit = 21 pens ÷ 3 = 7 pens
Number of red pens in the box at first = 1 unit = 7
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