How it works
To sort, look at two cards that sit side by side. If the bigger card is on the left, swap them. If they are already in order, leave them alone.
Go along the whole row, pair by pair. That trip is one pass.
Each pass sends the biggest card that is left over to its place.
Make pass after pass, and stop when a whole pass needs no swaps.
Worked examples
One pass
- The row is 4, 2, 5, 1, 3. Bo swaps 4 and 2, and the row is 2, 4, 5, 1, 3.
- 4 and 5 are in order, so he leaves them.
- He swaps 5 and 1, then 5 and 3.
- The row is 2, 4, 1, 3, 5, and the biggest card, 5, has floated to the end.
Pass two
- The row is 2, 4, 1, 3, 5. 2 and 4 stay.
- 4 and 1 swap, and 4 and 3 swap. 4 and 5 stay.
- The row is 2, 1, 3, 4, 5.
Pass three, and the check
- The row is 2, 1, 3, 4, 5. 2 and 1 swap, and the other pairs are in order.
- The row is 1, 2, 3, 4, 5.
- Pass four has no swaps at all, so the row is sorted. It took four passes.
A small row
- The row is 3, 1, 2. Pass one swaps 3 and 1 to give 1, 3, 2, then swaps 3 and 2 to give 1, 2, 3.
- Pass two has no swaps, so the row is sorted.
A taste of the worksheets
These are some of the questions on the sets. The printable sheets have more and an answer key.
- The row is sorted when a whole pass needs ___ swaps.
- Mix-up to fix: after one pass on 4, 2, 5, 1, 3, Jonah says, "2, 4, 1, 3, 5 is sorted, so I stop." What should he do? Keep making passes until a pass needs no swaps / Swap the 2 and the 4 back / Start again from the original row
- Which one is a step of sorting by hand? 🙃 swap two cards that are in order / 🔄 swap them when the bigger one is first / ⬇️ put the smallest card at the end
- Which one is not a step of sorting by hand? 🙃 swap two cards that are in order / ➡️ go along the whole row, pass after pass / 🛑 stop when a whole pass needs no swaps
- Which one is a step of sorting by hand? ☝️ stop after one pass every time / 🙃 swap two cards that are in order / 🎈 send the biggest card to the end each pass
Words to know
- pass
- One trip along the whole row, pair by pair.
- neighbors
- Two cards that sit side by side.
- swap
- Put two cards in each other's places.
- sorted
- In order, from smallest to biggest.
Watch out for
- Bo can only compare two cards at a time.
- Cards that are already in order stay put. Do not swap them.
- One pass may not be enough. Stop only when a whole pass needs no swaps.
- Random swaps do not sort a row.
Try it
In the row 2, 5, 3, do 5 and 3 swap?
Yes. The bigger card, 5, is on the left.
In the row 2, 5, 9, does Bo swap 5 and 9?
No. 5 is smaller than 9, so they are already in order.
After a pass, where does the biggest card end up?
At the end of the row. Each pass sends the biggest card that is left over to its place.
When is a row sorted?
When a whole pass needs no swaps. Then every pair is in order.
The row is 2, 1, 3. How many swaps in pass one?
1. 2 and 1 swap to give 1, 2, 3. 2 and 3 are already in order.
For grown-ups
Pick five things of different sizes. Mix them up in a row. Now sort them the robot way: look only at two neighbours at a time, swap them if the bigger one is on the left, and keep going along the row until a whole pass needs no swaps. Count the passes!
Play the Mission: pick five things of different sizes, mix them up in a row, and have your child sort them the robot way, looking only at two neighbors at a time, swapping when the bigger one is on the left. They keep going until a whole pass needs no swaps, and count the passes.