Which facts appear in the trench?

Additions of two numbers from 2 to 10, so sums up to 20, and subtractions from a number below 20. The subtraction never crosses into negatives, so a child who has not met those will not be ambushed by one at speed.

Is this just Car Rush with different numbers?

The steering and the three gates are the same engine, but the facts and the age are not. This one is grades 2 to 4 and drills adding and subtracting within twenty; Car Rush is grades 3 to 5 and drills the times tables. A child can be ready for one and years from the other.

She loves it but plays for twenty minutes straight. Is that useful practice?

It is useful for the first few minutes and pleasant after that, which is fine as long as you know which is which. Recall grows on short, frequent goes, so five minutes most days does more than a long run on Sunday.

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X Trench Run

Fly the trench, hit the right answer.

Grades 2-4 · Addition and subtraction facts at speed

How to play

1A fact appears, like 15 − 8 or 7 + 6.
2Three energy gates rush up the trench, each with a number.
3Fly your ship into the gate that matches. Arrow keys or the buttons.
4Right answer, more speed. Wrong one, a life lost. Three lives.

Try a few

9 + 5
Answer: 14
Make a ten on the way. 9 wants 1 to become 10, so take that 1 from the 5 and the 5 becomes a 4. Now it reads 10 and 4, which is 14. The only care needed is remembering the 5 is now a 4.
16 - 9
Answer: 7
Come down through ten. Take 6 off 16 to land on 10, which uses 6 of the 9. Three of the 9 are left, so take those too and land on 7. Two easy hops beat counting back nine times.
8 + 9
Answer: 17
Lean on a double. 8 and 8 is 16, and 9 is one more than 8, so the answer is one more than 16: 17. Near doubles turn a hard fact into a known one plus a single step.

Why this game helps

Addition and subtraction within twenty are the workhorse facts of early arithmetic, the ones every later method leans on, and like the times tables they have to become quick to be useful. A child reconstructing 15 − 8 from scratch every time is spending all their attention on the fact and has none left for the problem it belongs to. Flying a trench where the gate arrives on its own schedule forces the recall to keep pace, turning worked-out into remembered without the grind of flashcards. It pairs naturally with the slower, meaning-first games; this is the one that makes the facts fast.

If your child finds this hard

The most common wrong answer here is off by exactly one, which usually means the strategy is right and the bookkeeping slipped. A child making a ten for 9 + 5 moves 1 across and then counts it twice or forgets it moved, so 14 comes out as 15 or 13. The same slip appears coming down through ten, where 15 - 7 arrives as 9. The two wrong gates carry numbers within four of the right one, so an off-by-one answer is often sitting there waiting to be flown into.

Fix the bookkeeping rather than the fact. Ask your child to say both halves of the move out loud: nine and one is ten, and four is left, so fourteen. Naming what moved is what stops it being counted twice. A ten frame or two hands works as well as anything, because the one that crossed over stays visible.

If your child is still counting every fact on fingers, this trench is not the place yet. Fingers are a real method but a slow one, and a gate on its own schedule turns slow into guessing. Make Ten drills the bridge these facts depend on, and Addition Pop gives the same sums with no clock.

Common questions

Which facts appear in the trench?: Additions of two numbers from 2 to 10, so sums up to 20, and subtractions from a number below 20. The subtraction never crosses into negatives, so a child who has not met those will not be ambushed by one at speed.
Is this just Car Rush with different numbers?: The steering and the three gates are the same engine, but the facts and the age are not. This one is grades 2 to 4 and drills adding and subtracting within twenty; Car Rush is grades 3 to 5 and drills the times tables. A child can be ready for one and years from the other.
She loves it but plays for twenty minutes straight. Is that useful practice?: It is useful for the first few minutes and pleasant after that, which is fine as long as you know which is which. Recall grows on short, frequent goes, so five minutes most days does more than a long run on Sunday.

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