Measuring With Cubes

No gaps and no overlaps.

10 problems · about 12 minutes · 1.MD.A.2

What this lesson teaches

The child measures length by laying same-size cubes end to end with no gaps and no overlaps.

From earlier lessons. Loosen up before the new work.

6 problems

Review — Putting Three in Order: Ropes are 3, 9 and 6 cubes. How long is the longest?
Answer 9
Why 9 is the longest.
Review — Using a Third Thing: A rope is shorter than a string. The string is shorter than a pole. Is the rope shorter than the pole?
Answer Yes.
Why Rope is under string, string is under pole, so rope is under pole.
Review — Longer Than, Shorter Than: Why must you line up one end before comparing?
Answer Otherwise you cannot tell which is longer.
Why Lining up the ends is what makes the comparison fair.
Review — True or False to Twenty: Is 13 − 9 = 2 + 2 true?
Answer True. Both are 4.
Why Both sides come to 4.
Review — Missing Numbers to Twenty: 8 + ? = 12
Answer 4
Why 8 + 4 = 12.
Review — Take From Ten in Stories: 11 − 8 = ?
Answer 3
Why 11 − 8 = 2 + 1 = 3.

Straightforward practice. Get the method working first.

3 problems

A stick takes 6 cubes laid end to end. How long is it?
Answer 6 cubes
Why 6 cubes long.
What must be true about the cubes you measure with?
Answer They must all be the same size.
Why Units must be the same size or the count means nothing.
Ben left gaps between his cubes. Will his answer be too big or too small?
Answer Too small. He used fewer cubes than he should.
Why With gaps, fewer cubes cover the length, so the count comes out too small.

Mixed problems. Work out what kind of question it is before you start.

1 problem

Measuring a Book: Ana lays 8 cubes end to end along a book with no gaps. How long is the book?
Answer 8 cubes
Why 8 cubes end to end means 8 cubes long.