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Operations with Integers

A move each way

A cold room reads −7 °C (degrees Celsius). It warms by 3 degrees. What does it read now?

Start at −7.
Step 1 of 3
  1. Start at −7.
  2. Add 3. Walk 3 right.
  3. 7 is bigger than 3. Land on −4.

The room reads −4 °C now. The 3 steps right undo 3 of the 7 steps left. So 4 steps left remain.

A move's size is its number of steps. Its side is left or right.

Rule: a move each way? Take the smaller size from the bigger. Keep the bigger move's side.

Four pairs, a move each way
SumSizesBigger moveLands on
(−5) + 25 and 2left−3
5 + (−8)5 and 8left−3
(−2) + 92 and 9right7
6 + (−6)6 and 6neither0

Two equal moves cancel: one undoes the other. They end at 0, which is neither side.

Tap the side where the answer ends. Then watch the walk.

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This track

  1. 0 Start here
  2. 1 Two moves the same way
  3. 2 A move each way
  4. 3 Taking away, another way round
  5. 4 Two dashes on one line
  6. 5 Without the line
  7. 6 Checkpoint: adding and taking away
  8. 7 The same move, counted again
  9. 8 Past the end of the times table
  10. 9 Sharing it out
  11. 10 What zero does
  12. 11 Where we use them
  13. 12 Checkpoint: multiplying, sharing and zero
  14. 13 Zero pairs
  15. 14 The additive inverse
  16. 15 Many numbers, one sign
  17. 16 A number times a bracket
  18. 17 The big picture
  19. 18 Track quiz

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