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Math lesson plan · 2nd grade (Year 3 in England) · 30 minutes

Show length sums and differences on a number line

Measurement

CCSS 2.MD.B.6England: Y2 Measurement

Objective and success criteria

Students will: Show length sums and differences on a number line.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: Length story problems; Find numbers on a number line to 100

Leads to: the next skill in this area.

Materials: Rulers, scales and measuring jugs, Clock faces, Conversion chart, Mini whiteboards and pens, Printed student sheet (below).

Warm-up · 4 min

  • Quick retrieval from earlier learning (Length story problems; Find numbers on a number line to 100). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Sofia joins a 22 cm strip of paper and a 41 cm strip end to end. How long is the new strip? → 63Prompt: End to end means add the lengths.
  2. Noah has a 71 cm piece of string and cuts off 19 cm. How long is the piece that is left? → 52Prompt: Cutting off takes length away.
  3. Aisha joins a 40 cm strip of paper and a 40 cm strip end to end. How long is the new strip? → 80Prompt: End to end means add the lengths.

Hook · 3 min

  • Ask the class to estimate the length of the room or the weight of a bag before measuring it.
  • Share the objective: Show length sums and differences on a number line. Read the success criteria together.

I do: model it · 7 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Model one question from the student sheet, thinking aloud.
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 6 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.

You do: independent practice · 7 min

  • Students work on the student sheet. Circulate and check the first two answers of every student early.
  • Students who finish: write a question of their own for a partner, with the answer.

The 6 questions are on the student sheet below, with answers in the key.

Exit ticket · 3 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

Watch out for

  • Measuring from the end of the ruler instead of zero.
  • Converting units the wrong way (multiplying instead of dividing).

Support and stretch

Support

  • Review first: Length story problems.
  • Use concrete materials: rulers, scales and measuring jugs.
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

Free online practice with hints and printable worksheets for this skill: eurekami.com/math/grade-2.

Free lesson plan from eurekami.com/lesson-plan-builder

eurekami

Show length sums and differences on a number line

Name

Date

Score/ 6

  1. Question 1

    A ruler-line starts at 0 cm. A 16 cm ribbon is laid down, then a 20 cm ribbon after it. Where does the second ribbon end?

    1601020304050607080

    Answer

  2. Question 2

    On the number line, how many centimetres is it from 22 cm to 52 cm?

    01020304050607080901002252

    Answer

  3. Question 3

    A ruler-line starts at 0 cm. A 12 cm ribbon is laid down, then a 13 cm ribbon after it. Where does the second ribbon end?

    1201020304050607080

    Answer

  4. Question 4

    On the number line, how many centimetres is it from 21 cm to 53 cm?

    01020304050607080901002153

    Answer

  5. Question 5

    A ruler-line starts at 0 cm. A 11 cm ribbon is laid down, then a 7 cm ribbon after it. Where does the second ribbon end?

    1101020304050607080

    Answer

  6. Question 6

    On the number line, how many centimetres is it from 52 cm to 92 cm?

    01020304050607080901005292

    Answer

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Answer key: Show length sums and differences on a number line

  1. 1. 36

  2. 2. 30

  3. 3. 25

  4. 4. 32

  5. 5. 18

  6. 6. 40