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Math lesson plan · 2nd grade (Year 3 in England) · 45 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 · 5 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. Tariq joins a 40 cm strip of paper and a 19 cm strip end to end. How long is the new strip? → 59Prompt: End to end means add the lengths.
  2. Amara has a 95 cm piece of string and cuts off 75 cm. How long is the piece that is left? → 20Prompt: Cutting off takes length away.
  3. Jamal joins a 38 cm strip of paper and a 12 cm strip end to end. How long is the new strip? → 50Prompt: End to end means add the lengths.

Hook · 5 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 · 10 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 · 10 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 · 10 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 8 questions are on the student sheet below, with answers in the key.

Exit ticket · 5 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/ 8

  1. Question 1

    A ruler-line starts at 0 cm. A 28 cm ribbon is laid down, then a 21 cm ribbon after it. Where does the second ribbon end?

    2801020304050607080

    Answer

  2. Question 2

    On the number line, how many centimetres is it from 29 cm to 46 cm?

    01020304050607080901002946

    Answer

  3. Question 3

    A ruler-line starts at 0 cm. A 14 cm ribbon is laid down, then a 27 cm ribbon after it. Where does the second ribbon end?

    1401020304050607080

    Answer

  4. Question 4

    On the number line, how many centimetres is it from 39 cm to 57 cm?

    01020304050607080901003957

    Answer

  5. Question 5

    A ruler-line starts at 0 cm. A 23 cm ribbon is laid down, then a 30 cm ribbon after it. Where does the second ribbon end?

    2301020304050607080

    Answer

  6. Question 6

    On the number line, how many centimetres is it from 59 cm to 81 cm?

    01020304050607080901005981

    Answer

  7. Question 7

    A ruler-line starts at 0 cm. A 18 cm ribbon is laid down, then a 19 cm ribbon after it. Where does the second ribbon end?

    1801020304050607080

    Answer

  8. Question 8

    On the number line, how many centimetres is it from 21 cm to 66 cm?

    01020304050607080901002166

    Answer

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

  1. 1. 49

  2. 2. 17

  3. 3. 41

  4. 4. 18

  5. 5. 53

  6. 6. 22

  7. 7. 37

  8. 8. 45