Decimals on the number line

The idea

A decimal number lies between the whole numbers on either side of it; to locate it, the unit between them is divided into 10 equal parts and as many parts are taken as it has tenths.

Where is 1.4?

The number 1.4 is 1 unit and 4 tenths.

Where does 1.4 lie on a number line?

• Between 0 and 1
• Between 1 and 2
• Between 4 and 5

Find it on the line

Place each number. First tap the part of the line between the two whole numbers it lies between. Then tap its mark.

Between two whole numbers

A decimal number has a whole part and some tenths. The whole part tells which unit it is in. The tenths tell how far into that unit.

A decimal number lies between the whole numbers on either side of it. To locate it, the unit between them is divided into 10 equal parts, and as many parts are taken as it has tenths. 1.4 lies between 1 and 2.

• Decimal | Lies between | Parts counted
• 1.4 | 1 and 2 | 4 tenths
• 3.7 | 3 and 4 | 7 tenths
• 0.9 | 0 and 1 | 9 tenths

Notes

A decimal lies between the two whole numbers around it. Divide that unit into 10 equal parts and take as many parts as it has tenths.

Check yourself

Between which two whole numbers does 5.8 lie?

To place 7.5, the unit from 7 to 8 is divided into how many equal parts?

Answer: 10

10 equal parts. Then we count 5 of them from 7.

To place 7.5, how many of these parts do we count from 7?

Answer: 5

5 parts from 7, so 7.5 is exactly in the middle of 7 and 8.

Which of these lies closest to 3, just before it?

• 5 and 6 — correct. Yes! The whole part is 5, so it lies in the unit from 5 to 6.
• 4 and 5. 5.8 is bigger than 5. It has passed the 5 mark.
• 8 and 9. The 8 is the tenths digit. The whole part is 5.
• 2.1. 2.1 has only gone 1 tenth into the unit from 2 to 3.
• 2.5. 2.5 is in the middle of the unit from 2 to 3.
• 2.9 — correct. Yes! 2.9 is 9 tenths into the unit from 2 to 3. Only one tenth short of 3.