Measuring length
Order three objects by length and compare the lengths of two objects indirectly using a third object
What a learner can do afterwards
- Put three ribbons in order from shortest to longest
- Use a piece of string to compare the heights of two objects that cannot be placed side by side
- Explain that if A is longer than B and B is longer than C, then A is longer than C
The lesson
You already know how to tell if one thing is longer than another. Now you will learn two new tricks: putting three things in order, and comparing two things that cannot sit side by side.
Mia has three pencils. She lines up the red pencil next to the blue pencil and sees the red one is shorter. Then she lines up the blue pencil next to the green pencil and sees the blue one is shorter too. So the order from shortest to longest is red, blue, green.
Here is a shortcut: if one thing is longer than a second thing, and that second thing is longer than a third thing, then the first thing is longer than the third one too. You do not need to compare the first and the third directly.
To order things, compare them two at a time. And remember, if A is longer than B, and B is longer than C, then A is longer than C too.
Watch it
Where it sits
Learn first
Where this leads
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.