Dewey's Ten-Tank — Make a Ten and Some Ones (Kindergarten)

About this activity

Dewey the duckling fills a pond-tank with glowing bubbles, and when the tenth drops in, ten bubbles seal into one shimmering ten-raft while the leftovers become the "and some more" — so 13 or 17 shows up as a ten and some ones, recorded as 10 + N. The child composes, decomposes, regroups, and compares teen numbers. It's a free, interactive Kindergarten place-value activity that runs in the browser with no account.

The heart of the activity is watching ten ones become a single unit of ten. That sealing moment is exactly what place value asks young children to understand: a teen number is one ten plus some extra ones, not just a pile counted to seventeen. Because the child builds, decomposes, and compares the same numbers in different ways, the idea is approached from several angles instead of memorized one way.

It is aligned to Common Core K.NBT.A.1 — composing and decomposing numbers from 11 to 19 into a ten and some further ones, and recording each as a ten and ones. No timer, no score — just calm, playful practice.

What's inside this activity

• Designed for Grade K learners (ages about 5–6)
• Common Core strand: Number & Operations in Base Ten
• Aligned to Common Core standard K.NBT.A.1

How to play

Read or listen to the target number for the round.

Drop bubbles in until ten seal into a ten-raft, then add the leftover ones, and check that it reads 10 plus some more.

Not quite? Add or remove bubbles and try again — there is no timer and no score.

What your child practices

• Building a teen number as a ten-raft and some loose bubbles
• Taking a teen number apart into a ten and some ones
• Regrouping ten loose ones into a single ten
• Comparing two teen numbers by their tens and ones

Learning goals

Compose and decompose teen numbers as a ten and some ones — the focus of Common Core K.NBT.A.1

Understand ten ones as one unit of ten

Build the place-value foundation for two-digit numbers in first grade