Choose a practice card
Use the buttons or Tab and Enter/Space. The drawing is repeated in words below it.
Your model
0 tens and 0 ones make 0
Choose pieces, then check your model. You can try as many times as you need.
Why a trade works
Ten loose ones and one full strip show the same amount. An exchange changes the pieces, not the total.
For a no-screen route, use the plain-text and print cards. A teacher can provide real ten-strips and counters. Ask for large or tactile pieces if helpful.