Number Concepts to 20
Warm-up
Flash a double ten-frame briefly: full left frame plus some on the right. Ask: How many? How did you know? Try quantities 11-19. Ask: What do you always see in the left frame? (Always 10.)
Explore
Pairs roll a number cube, move along a number line 0-20, and say each landing number as ten and ___. When above 10, the ten-frame is full; below 10 it is not. Ask: How many more to reach 20?
Formalize
Number talk: show 13 on a double ten-frame. Ask: How do you see this? What is the 10? What are the 3? Record: 13 = 10 + 3. Then: if I add 2 more, do I need to count from the start? Connect to counting on: 13 ... 14, 15.
Number Concepts to 20
Pull out the hundred chart. Skip-count by 2s together colouring each landing square. What pattern do you see? Then skip-count by 5s with a second colour. Connect both patterns to the base 10 structure of the chart.
Practice
Students build numbers 11-20 on double ten-frames, record them as __ and __, and write the numeral. Exit ticket: show a double ten-frame with 16 and students write the number and say ten and ___.
Exit ticket
Students build numbers 11-20 on double ten-frames, record them as __ and __, and write the numeral. Exit ticket: show a double ten-frame with 16 and students write the number and say ten and ___.
Step 1: Count out 17 counters onto a double ten-frame. The top frame fills completely (that's 10) and the bottom frame shows 7 more.
Step 2: Say the three names together: seventeen; ten and seven more; 17. Point to each representation as you say its name so students link word, quantity, and numeral.
Step 3: Ask: "If I cover the bottom frame, how many are hiding?" Students should answer 7 without recounting the top frame — the full frame is trusted as ten.
Why it matters: students who see 17 as "ten and seven" are already doing place value; students who see it only as a count of seventeen ones will struggle in Grade 2.
What you see: asked "how many?" after adding one more counter to 16, the student recounts the whole pile from 1.
Step 1: This is not a counting error — it tells you the student hasn't yet trusted that the last number said IS the quantity (cardinality) or can't yet count on.
Step 2: Cover the counted pile with your hand and say: "There are 16 under my hand. Here is one more. How many now?" Covering blocks the recount and invites counting on.
Step 3: If the student still needs to see all the counters, practice with very small piles first (cover 4, add 1) where their confidence is high, then grow the covered amount.
What NOT to do: don't just tell them "start from 16." The behaviour changes but the understanding doesn't.
What happened: the student heard "fif-teen" as two numbers — a 10 and a 5 — and wrote them side by side: 105.
Step 1: Validate the thinking: they DO know fifteen is ten and five. The error is in recording, not understanding. This is actually a good sign.
Step 2: Build 15 on a double ten-frame: one full frame (10), one frame with 5. Then show how the written numeral compresses this: the 1 in 15 stands for the one full frame, the 5 for the five extras.
Step 3: Practice with arrow cards (a 10 card and a 5 card that physically slide together to make 15) so students see the 10 "hiding" behind the 5.
Check: ask them to write eighteen. If they write 108, repeat with frames; if 18, the compression idea has landed.