3
Numbers on a scale
Learner’s Book 1: Unit 12, pp. 174–175
GoalUse the numbers on a ruler and on a measuring jug to measure.
New words
scale · numbers in a row on a measuring toolruler · a tool for measuring lengthmeasuring jug · a jug with numbers up its side
Explanation
Many tools have numbers in a row. We call this a scale. A ruler has a scale for length. Always start at 0: put one end of the object at 0, then read the number at the other end. A measuring jug has a scale up its side for capacity. The higher the water, the bigger the number. To read a jug, look at the top of the water and read the number beside it. A ruler with numbers is much easier to use than a plain strip.
Worked examples
The leaf starts at 0 and ends at 9. The leaf is 9 cm long.
Two jugs are the same size. The jug with the higher water has more juice in it. In this picture, the second bar is longer, so the second jug has more.
A plain strip with no numbers does not tell us how long things are. We choose a ruler with numbers.
Class activity
Pour and read: use a clear cup or jug that has numbers. Pour in some water. Read the number at the top of the water. Then pour in a little more. Did the number get bigger? Draw what you saw.
Practice
1
How long is the line?
7 cm
2
How long is the line?
5 cm
3
The three bars are three jugs of the same size with water. Put them in order from the least water to the most: top, middle, bottom.
middle, top, bottom
4
When we measure with a ruler, which number do we start at?
0