Cogito
Grade 2 Math · Chapter 7 · Lesson 8
Line Plots
Marks stacked over a number scale.
10 problems · about 13 minutes · 2.MD.D.9
What this lesson teaches
The child builds and reads a line plot of measurement data with a whole-number scale.
- A line plot puts one mark above the number measured.
- The labels are a number scale, so their order is fixed.
- An empty column means nothing measured that.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
3 problemsReview — Bar Graphs: Bars of 10 and 6. How many more is the first?
Answer 4
Why The difference is 4.
Review — Picture Graphs: 5 apples and 8 fish. How many more fish?
Answer 3
Why There are 3 more fish.
Review — Money Problems: Pay 75¢ for a 55¢ item. What is the change?
Answer 20
Why The change is 20¢.
Warm Up
Straightforward practice. Get the method working first.
3 problems2 marks at 4, 5 at 5, 1 at 6. How many things in all?
Answer 8
Why 2 + 5 + 1 = 8.
What does one × stand for?
Answer One thing that was measured.
Why Each mark is one measurement, and its position gives the length.
1 mark at 4, 3 at 5, 4 at 6. How many things in all?
Answer 8
Why Add the stacks.
Build It Up
The same ideas with more to keep track of.
1 problem3 marks at 5 and 4 at 6. How many more measured 6?
Answer 1
Why 4 − 3.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
3 problemsCan you reorder the numbers on a line plot?
Answer No. They are a number scale.
Why Compare with a bar graph.
Reading the Plot: A plot has 4 marks at 6 cm and 2 at 7 cm. How many pencils were 6 or 7 cm?
Answer 6 pencils
Why 4 + 2 = 6 pencils.
The Empty Column: A column at 8 cm has no marks. What does that mean?
Answer Nothing measured 8 cm.
Why An empty column means no object had that length.