Apps

Crab Math Run

No ads, no accounts, nothing collected.

Math practice built to keep kids playing. A crab walks a pier over the sea, and the math problem rides inside the sun. Answer it and the parrot flies a plank across the gap.

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No ads. Nothing collected.

  • No accounts, no sign-in, and nothing is collected. Progress stays on the device.
  • One purchase. No in-app purchases, no ads, no subscriptions.
  • Plays without an internet connection.

Read the privacy policy for Crab Math Run.

What a run looks like

The crab stands on the pier under a sun that holds the problem 2 plus 9. A plank behind the crab reads 5 plus 8 equals 13, and a number keypad sits on the right.
The problem rides inside the sun, and every answered fact stays written on its plank.
The parrot flies out of the sun carrying a plank toward the gap in the pier while the crab waits and fish swim below.
A right answer sends the parrot out with a plank.
The cash out screen after a run: accuracy 100 percent, average answer 12.1 seconds, longest streak 3, 21 shells earned, turned into 3 gems.
Every run ends with a summary, and shells become gems.
Deep in the player's sea, an orca asks the sum 2 plus 1, with three bubble answers to choose from.
Super creatures in the deep ask sums of their own.
The crab rides the boat at the end of the pier at dusk, above a sea of fish, a seahorse and a starfish.
At the end of a run the boat comes in.
The home screen: the crab on the pier, a Play button, and the chosen settings for addition, numbers 0 to 9, steady speed and relax mode.
Pick the sign, the numbers, the speed and the kind of run, then play.

You pick the math

  • Addition, subtraction, multiplication and division: one sign, plus and minus, times and divide, or all four.
  • Three levels: numbers 0 to 4, 0 to 9, and 0 to 12.
  • A custom range anywhere from 0 to 20, or one number to drill, like the sevens.
  • Four speeds, from 15 seconds a problem down to 4.
  • Type the answer on a keypad, or pick from four choices.
  • Every fact in the range comes up once before any repeats.

A wrong answer doesn't end the run

In Safe mode, the default, a missed problem still gets its plank, with the whole fact written on it, and the hero never falls.

Splash mode is there for players who want stakes: the boards run out, the hero goes in, and the boat pulls him out with a rope ladder every time.

Crab Math Run never ends a run on a miss in its default mode, because a kid who is afraid of being wrong can stop trying.

Ways to play

  • Timed runs of 1, 2 or 5 minutes.
  • Relax, with no clock: the boat comes the moment you call it.
  • Flash cards for pure study, with the answer on the back.
  • Every fact you miss is kept in one list, and two right answers in a row take it off.

Spend the gems you earn

Gems come only from right answers, and they cannot be bought.

They dress the pier and the seabed: 11 things for the pier, 10 for the sand, flags for the boat, snails, and food for the fish.

Thirteen kinds of sea life join your water as your gems add up.

Pick your hero: a crab, an octopus or a snail.

For parents and teachers

  • Every run ends with a summary: accuracy, average answer time, longest streak, and what was earned.
  • The Records book keeps a page for every kind of run.
  • Every fact you miss is kept in one list, and two right answers in a row take it off.

Where it runs

iPhone, iPad, Android, Kindle Fire. iPhone and iPad need iOS 15.0 or later.

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