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Subtraction Speed Test
Subtraction is where most people slow down. Race live opponents through twenty subtraction problems in two minutes and build the kind of fast, automatic recall that makes everyday maths easy.
Free, no sign-up needed. 20 problems, 2 minutes.
What the problems look like
17 − 9
20 − 13
15 − 8
18 − 4
Tricks to get faster
- →Count up instead of down: for 17 − 9, go from 9 to 10 (1) and on to 17 (7), so the answer is 8.
- →Subtract through ten: 15 − 8 is 15 − 5 − 3, which is 7.
- →Check with addition: if 20 − 13 = 7, then 7 + 13 should be 20.
How the race works
- 1. Join a raceYou are matched with up to four other racers. If nobody is online, computer racers matched to your level fill in.
- 2. Type and press EnterEvery correct answer moves your car forward. A wrong answer keeps you on the same problem.
- 3. Climb the ranksYour speed (problems per minute) and finishing place update your ELO rating, from Beginner to Grandmaster.
Questions
Can answers be negative?
No. The bigger number always comes first, so every answer is zero or more.
How is my score calculated?
Your speed is problems per minute (PPM) across the race. Your finishing position against the other racers updates your ELO rating.
Is there a practice mode?
Yes. Practice runs the same twenty problems with no opponents, so you can warm up before racing.