courses › Pre-Algebra

Add, subtract, multiply, and divide with signs.

Best in your head · no pen, no calculator why?

Learn first (about 3 minutes)

Opens at level 9.

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Builds on: Two-digit add & subtract (not open yet)

skills · practice stats

From rounds of this course only: box, review and trial answers are left out. Once a skill has 40 tries, it compares your first 20 tries with your last 20.

• Add & subtract with signs par 6 s not tried yet

  worked example

  −10 − (−17)

  Answer: 7

  1. Subtracting a negative is adding: −10 − (−17) = −10 + 17.
  2. The signs differ: 17 − 10 = 7, and 17 is farther from zero, so the answer is 7.

• Multiply & divide with signs par 5 s not tried yet

  worked example

  (−6) × 8

  Answer: -48

  1. 6 × 8 = 48.
  2. The signs differ, so the result is negative: −48.

• Absolute value par 7 s not tried yet

  worked example

  |−13| − |−12|

  Answer: 1

  1. Each number has its own bars, so take each absolute value first: |−13| = 13 and |−12| = 12.
  2. Then 13 − 12 = 1.

rest ladder

Win 3 of your last 4 rounds and the course rests. A win is 90% right, within 2× the round's par. Pass the review when it comes back and the next rest is longer.

1. 1 day
2. 3 days
3. 7 days
4. 14 days
5. 30 days
6. 60 days
7. mastered · every 90 days

your rounds

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