1.2 Measuring accurately
To measure accurately, line up one end of the pen with the 0 mark on the ruler. If there is no 0 mark, use the end of the ruler. Hold the ruler straight against the pen. Which mark does the other end come to?
Hint: Be careful with the bit of ruler or tape measure that comes before the first mark! Make sure you line up whatever you’re measuring with the ‘zero’ mark.
You can see from this diagram that the pen is 15 cm long.
Now try the following activity. Remember to check your answers once you have completed the questions.
Activity 3: Building a shelf for DVDs
- You want to build a shelf to hold some DVDs. You need to make sure that it’s big enough! How tall is a DVD case?
Figure 2 Measuring a DVD case
- You have run out of screws. Before you go to buy some more, you need to measure the last screw you have to make sure you buy some more in the same size. How long is this screw?
Figure 3 Measuring a screw
- How far is it across the head of the screw?
Hint: Draw lines from the edge of the screw head down to the ruler to help you measure it.
Figure 4 Measuring a screw head
Answer
- The DVD case is 19 cm tall.
Figure 5 Measuring a pen (answer) - The end of the screw is halfway between 2 and 3 cm, so the screw is 2.5 cm (2
cm) long. Note here how the measurement is not a whole number. Often items have to be measured very precisely: when this is the case, it may not be appropriate to round off to the nearest centimetre, for instance.
Figure 6 Measuring a screw (answer) - The screw head is 5 mm wide.
Figure 7 Measuring a screw head (answer)
OpenLearn - Everyday maths 1 (Northern Ireland) 
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