A dusk slate ridge, frost stones, and a bronze ibex. When the ones digit cannot take the subtraction, tap the tens crag to crack a ten. Ten pebbles tumble to the ones ledge. Then write the ones digit and the tens digit on the number pad. Built for third-grade two-digit subtraction with borrowing.
Pick a Ridge
Easy is 90 seconds and one-digit subtrahends. Medium is 70 seconds and always borrows. Hard is 50 seconds with mixed problems.
Read the Slate
A cream slate shows a vertical two-digit subtraction. The crag holds a tens boulder and an ones ledge of pebbles.
Borrow if Needed
When ones cannot take the number below, tap the glowing tens crag. Ten pebbles fall to ones. If ones is already enough, do not tap the crag — write the ones digit.
Write Ones, Then Tens
Tap digits on the pad. A hit flies points off the ridge. A miss shakes the crag and costs a life. Chase a new best before time runs out.
Crack the Ten
If ones is too small, the tens boulder glows. Tap it to split a ten. The tens digit is crossed out and ones becomes ten more.
Write Each Place
After the borrow is settled, tap the ones digit, then the tens digit. Each correct place pops hundreds of points. A wrong digit or a skipped borrow costs a life.
Score, Streak, and Lives
Hits pay in hundreds and grow a combo. A miss resets the streak. Best score is saved per difficulty.
Three Ridges
Easy is two-digit minus one-digit. Medium always needs a borrow. Hard mixes problems and shortens the clock.
Crag Borrow is a two-digit subtraction game for second through fourth graders. A slate ridge holds a vertical subtraction problem. When the ones place cannot subtract, the player taps the tens boulder to crack a ten. The tens digit drops by one and ones grows by ten, shown as pebbles on the ledge. The player then writes each place on a number pad. Correct digits award points in the hundreds. Wrong digits and missed or extra borrows reset the streak and cost a life. Buttons and labels follow the site locale.
See the Borrow
The cracked ten is not a footnote. Stones move from the tens ledge to the ones ledge so regrouping is visible.
Instant Feedback
A hit pops points off the crag. A miss shakes the ibex. Scoring is not hidden behind an OK step.
Place by Place
Players write ones first, then tens, the same order as column subtraction on paper.
Built for Touch
Play sits under the board. The number pad sits under the crag so nothing covers the slate or the stones.
Tap it only when the top ones digit is smaller than the ones digit you are subtracting. That is a borrow. If ones is already large enough, skip the crag and write the ones digit.
If you tap a number before cracking a needed ten, you miss, the streak resets, and you lose a life.
That is also a miss. Ones can already take the subtraction, so the extra crack costs a life.
Yes. The score row sits above the ridge. The number pad sits below it, so the slate and the crag stay clear on a narrow screen.
Second through fourth grade, when students learn two-digit subtraction with regrouping. Stay on Easy for two-digit minus one-digit. Use Medium when every problem needs a borrow.