Leaderboards
Overflow a real round with at least five pops and post your count under a nickname. Sums to 10 and sums to 20 each keep their own board, and every board holds the 100 highest counts of the day, the week, the month, and the year. A nickname is all that is required; a state or country is optional, and the game never asks for anything more. Practice rounds stay on your device.
Top 100 rounds on the Sums to 10 addition facts, most bubbles popped first. Resets at midnight, US Eastern time.
No rounds on this board today yet. Pop some bubbles and post the first score.
How to Play
Choose a range, sums to 10 or sums to 20, and press Play or the Enter key. Seven bubbles float up and the water begins to climb, but only one bubble glows: the oldest one in the tank. Type its sum. There is no bubble to search for and no Enter key between digits — the moment your answer could not be anything else, the bubble pops, the glow jumps to the next oldest bubble, and a new one floats up a beat later to fill the empty spot.
Here is exactly what to type. Each key below is one press.
One digit. Press 9 and the glowing bubble pops right away.
Two digits, only in sums to 20. Press 1 and then 5; the bubble waits for both before it pops.
9 + 4 is 13, not 12. Once both digits land the tank checks, finds no match, and the water rises a little — the same bubble keeps glowing.
- Drain the tank to clear a stage
Pop faster than the water climbs and the level reaches the floor. The plug opens, the tank empties, the stage is cleared, and it refills a little higher with a faster pump. A short streak will do it on the first stage.
- Three in a row drains the tank further
Three correct answers with no miss between them drop the water an extra step with a swirl. A wrong answer adds a splash and starts the streak over.
- The golden bubble
Once you have popped a handful, a golden bubble shows up now and then. Answer it while it glows and every bubble in the tank pops with it.
- The water speeds up
An untouched tank overflows in about half a minute, and the pump runs faster the longer a round lasts and with every stage cleared, so every round ends somewhere. The score is what you popped first.
Why Only One Bubble Glows
Most sums here fit in a single digit, and a handful of others run to two. Handing a learner seven bubbles and letting any one of them pop would mean a lot of accidental pops on the wrong fact, so Addition Bubble Tank picks for you: the bubble that has floated longest lights up, and that is the one on the clock. Getting it right passes the glow to whichever bubble is next in line, so the tank always clears in the order the bubbles arrived, like a queue nobody can jump.
The other six bubbles are not decoration. A learner still reads every sum floating past while waiting a turn, which is its own kind of rehearsal, and a fact that keeps resurfacing without ever being the one that is glowing is a fact worth a second look once the round ends.
Keyboard, Keypad, and Sound
A computer keyboard works with either the number row or the numeric keypad, and every press lights the matching key on the on-screen keypad so a child watching along can follow. On a phone or tablet, that on-screen keypad is the only input needed — it is the same one Math Builders uses during practice, and the game never pulls up the device's own keyboard over the tank.
A handful of short, watery sounds mark the big moments: a pop, a splash for a miss, a gurgle when the plug opens, and a low note if the duck goes under. The speaker icon mutes all of it, the choice sticks on that device, and nothing plays before the round starts.
Using Addition Bubble Tank in Class or at Home
Addition Bubble Tank is a game, not a diagnostic. It rewards knowing which sums come easily under a rising clock; it does not tell you which ones are shaky on an ordinary day. For steady, printable review, see addition worksheets covering the same ranges, and for what fluency means at this age and how to build it, read addition and subtraction fluency. The game works alongside that kind of practice; it is not a replacement for it.
For a different kind of round, the Addition Speed Grid fills a shuffled chart while a snake follows your path, and its multiplication counterpart, Bubble Tank, pops products instead of sums. See every game on the addition games hub, or browse every operation on free math games.
Frequently Asked Questions
Drain the tank before it overflows. Answer the glowing bubble to pop it and the water drops a step; keep popping faster than the pump fills and the level reaches the floor, the plug opens, and the stage is cleared. The tank refills a little higher with a faster pump, and every round ends in an overflow eventually. Your score is the bubbles popped and the stages cleared.
Only the one that glows. Seven bubbles float at once, but the oldest one lights up, and that is the sum to type. Get it right and the glow moves to whichever bubble has been waiting longest; a fresh bubble floats up to fill the empty spot a moment later.
The water rises a little and your streak of correct answers starts over, but the same bubble keeps glowing until you answer it. Backspace removes a digit before the sum is checked; a sum is only judged once you have typed as many digits as it has.
A rare bubble that appears once you have popped a handful. Answer it while it glows and every bubble in the tank pops at once, each one adding to your score.
The tank is sealed with a glass lid, and a rubber duck rides on the surface of the water. As the level climbs, the duck rises with it and the edges of the tank glow red; if the water reaches the lid, the duck flips over and sinks, and the round ends there.
Yes. Turn on Practice before pressing Play. The water climbs at about a third of its normal pace and never reaches the lid, and you end the round yourself with the flag button whenever you like. Practice rounds never post to a leaderboard.
After a real round overflows with at least five pops, post your count under a nickname and, if you like, a state or country. There is a separate board for sums to 10 and sums to 20, each keeping the 100 highest counts of the day, the week, the month, and the year in US Eastern time. Nicknames pass through a word filter, and the game never asks for a real name, a town, or an email address.