Measures
Drawing and measuring lines
In this unit you measure lines in centimetres and draw your own lines with a ruler. You always start at 0, and you can use your ruler like a number line.
Start at 0
When you measure a line, put the 0 on your ruler at the start of the line. Read the number at the other end of the line. That number is the length in centimetres. A line from 0 to 6 is 6 cm long.
Longer and shorter lines
To compare two lines, measure each one and compare the numbers. The line with the bigger number is longer. The line with the smaller number is shorter.
Drawing a line
To draw a line of a chosen length, put your ruler down and start at 0. Draw along the ruler and stop at the number you want. To draw a 5 cm line, start at 0 and stop at 5.
The ruler as a number line
A ruler works like a number line, with the numbers in order. You can jump along it to add or subtract. To find how far you jumped from 3 to 9, work out 9 - 3 = 6. When you make strips 5 cm shorter each time, keep subtracting 5: 20, 15, 10, 5.
Worked examples
Measure a line from 0
- Put the 0 of the ruler at the start of the line.
- Look at the number at the other end.
- The line ends at 6.
Answer: The line is 6 cm long.
Compare two lines
- Line A is 9 cm and Line B is 4 cm.
- Compare the numbers: 9 is more than 4.
- So Line A is longer and Line B is shorter.
Answer: Line A (9 cm) is the longer line.
Draw a line of a given length
- Start your ruler at 0.
- You want a 5 cm line, so find the 5 mark.
- Draw the line from 0 up to 5.
Answer: The line ends at 5, so it is 5 cm long.
Make each strip 5 cm shorter
- Strip 1 is 20 cm.
- Take 5 cm off for the next strip: 20 - 5 = 15.
- Keep going: 15 - 5 = 10, then 10 - 5 = 5.
Answer: The strips are 20 cm, 15 cm, 10 cm and 5 cm.
Where you see this in real life
- Drawing a straight line of an exact length for a picture or a chart.
- Making paper strips that each get 5 cm shorter to build a set of rings.
- Using a ruler like a number line to jump from one number to another.
Key words
- Line
- A straight mark drawn with a ruler.
- Ruler
- A tool with centimetre marks used to measure and draw lines.
- Centimetre (cm)
- A small unit of length used for measuring lines.
- Longer
- Having a bigger length.
- Shorter
- Having a smaller length.
- Number line
- A line with numbers in order that you can jump along to add or subtract.