Quick times 5, 25 and 125
A shop packs 44 boxes. Each box holds 25 pens. How many pens is that?
Step 1 of 4
- A bar for 100.
- Cut it into 4 parts. Each part is 25.
- 44 × 100 = 4,400.
- Share 4,400 into 4. You get 1,100.
There are 44 × 25 = 1,100 pens.
The rule
25 is 100 shared into 4 parts: 100 ÷ 4 = 25. To share equally is to divide. So times 25 means times 100, then share into 4. The same idea works for 5 and 125.
Times 5 is times 10, then half. Times 25 is times 100, then a quarter. Times 125 is times 1000, then an eighth.
| Times | Do this | Example |
|---|---|---|
| 5 | × 10, then half | 18 × 5: 180, then 90 |
| 25 | × 100, then a quarter | 44 × 25: 4,400, then 1,100 |
| 125 | × 1000, then an eighth | 24 × 125: 24,000, then 3,000 |
Do the times first. The share then comes out whole. 10 ÷ 2 = 5, 100 ÷ 4 = 25, 1000 ÷ 8 = 125.
Factors are the numbers in a product. Look for two factors whose product is 100 or 1000. 4 × 25 = 100. So 4 × 13 × 25 = 13 × (4 × 25) = 13 × 100 = 1,300.
Tap the quickest way in the lab.
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