A whole and a part, in one number
Show on a big screenA jug holds 2.9 L, litres, of water. How do you write that as a fraction?
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- Three strips. Each is 1 L, cut into ten parts.
- Shade two whole strips. That is 2.
- Shade 9 parts of the third strip. That is 9/10.
- Together: 2 9/10, or 29/10, or 2.9.
The rule
A decimal is its whole part plus a fraction. So 2.9 is 2 and 9/10.
A whole and a fraction, side by side, is a mixed fraction.
The digits after the point are the top of the fraction. The bottom is 1, then a zero per digit after the point.
In 2.9, the fraction part has top 9. One digit after the point gives bottom 10.
Count every part and you get one fraction. 2.9 is 29 tenths, so it is 29/10. 2 wholes are 20 tenths, and 20 + 9 = 29.
Going back works too. 83/10 is 83 tenths. Ten tenths make a whole. 83 ÷ 10 = 8, with 3 left. So 83/10 is 8 3/10, which is 8.3.
| Decimal | Mixed fraction | One fraction |
|---|---|---|
| 2.9 | 2 9/10 | 29/10 |
| 6.35 | 6 35/100 | 635/100 |
| 4.07 | 4 7/100 | 407/100 |
| 1.206 | 1 206/1000 | 1206/1000 |
Watch out!
9 4/10 means 9 plus 4/10. It does not mean 9 times 4/10. So 9 4/10 is 9.4, not 3.6.
Try the lab to finish this lesson.