Lesson 7 of 15
Two names again
Show on a big screen7/4 of a metre of rope. How do you write that as a decimal?
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Step 1 of 3
- One whole, split into 4 equal quarters. Each quarter is 25 squares.
- Shade 3 of the 4 quarters. That is 75 squares.
- 75/100 is 3/4, which is 0.75.
The rule
As a decimal, 7/4 of a metre is 1.75 m.
A decimal is a fraction. Its bottom is 10, 100, 1000 or more.
Ask what number turns the bottom into 10, 100 or 1000. Multiply top and bottom by that number.
The method works for 1/4 and 3/5. The method does not work for 1/3. No number turns a bottom of 3 into 10, 100 or 1000. 10, 100 and 1000 are not in the 3 times table.
For 7/4, the number 25 turns the bottom 4 into 100.
7/4 = (7 × 25) / (4 × 25) = 175/100 = 1.75. 175 hundredths is 1 whole and 75 hundredths.
The fraction name is quicker when the sharing is easy. 0.75 of 8 m is 3/4 of 8 m. One quarter of 8 m is 2 m. So three quarters are 3 × 2 = 6 m.
| Decimal | Fraction | Sum | Answer |
|---|---|---|---|
| 0.75 | 3/4 | 0.75 of 8 | 6 |
| 0.5 | 1/2 | 0.5 of 8 | 4 |
| 0.6 | 3/5 | 0.6 of 20 | 12 |
Try the lab to finish this lesson.