3 Addition and subtraction on the number line

Watch the video below to see how you can use a number line to help you with addition and subtraction involving negative numbers.

Transcript (opens in new window)

See how you get on in this next activity.

Activity 3 Working with negative numbers

Allow approximately 10 minutes

Try the following examples. Start by drawing your own number line from –10 to + 10.

  1. 3 − 7

Answer

  1. Start at 3, move 7 units to the left.
Moving 7 units to the left from 3 to –4.
Figure 7 Number line for Activity 3, part (a)

Thus, 3 − 7 = –4.

  1. (–2) + 5

Answer

  1. Start at –2, move 5 units to the right.
Moving 5 units to the right from –2 to 3
Figure 8 Number line for Activity 3, part (b)

Thus, (–2) + 5 = 3.

  1. (–3) − 6

Answer

  1. Start at –3, move 6 units to the left.
Moving 6 units to the left from –3 to –9.
Figure 9 Number line for Activity 3, part (c)

Thus, (–3) − 6 = –9.

  1. (–4) + 2

Answer

  1. Start at –4, move 2 units to the right.
Moving 2 units to the right from –4 to –2.
Figure 10 Number line for Activity 3, part (d)

Thus, (–4) + 2 = –2.

Well done for completing your first calculations using negative numbers. These examples all involved subtracting or adding positive numbers to a negative number. Things become slightly more challenging when looking at adding and subtracting negative numbers, but again you’re going to call in your trusty number line to help.

OpenLearn - Succeed with Maths – Part 1
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