Cogito
Grade 1 Math · Chapter 6 · Lesson 3
Putting Three in Order
Shortest, middle, longest.
10 problems · about 10 minutes · 1.MD.A.1
What this lesson teaches
The child orders three objects from shortest to longest.
- Compare two at a time.
- Find the shortest, then order the rest.
- Shortest, middle, longest.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
5 problemsReview — 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.
Warm Up
Straightforward practice. Get the method working first.
3 problemsRopes are 3, 9 and 6 cubes. How long is the longest?
Answer 9
Why 9 is the longest.
How much longer is a 9-cube rope than a 3-cube one?
Answer 6
Why 9 − 3 = 6.
Sticks are 5, 8 and 2 cubes. How long is the longest?
Answer 8
Why Which is biggest?
Build It Up
The same ideas with more to keep track of.
1 problemStraws are 7, 4 and 6 cubes. How long is the shortest?
Answer 4
Why Which is smallest?
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
1 problemThree Ribbons: Ribbons are 6, 3 and 9 cubes long. How long is the shortest one?
Answer 3 cubes
Why 3 is the smallest, so that ribbon is shortest.