Lesson 8 of 8 in this sequence

100%

Not completed yet

Saved on this device only — not synced to an account yet.

Learning path

Step 8 of 8

End of sequence

ResumeReturn to this step ReviewRevisit the core idea RemediateGet repair practice

Completion

Review objectives and instruction
Complete the activity with manual learner confirmation
Answer every understanding-check item
Show completion feedback and reward only after the learner finishes the check

Progress

Step 8/8
14 content types
AI help source context available
Auto-advance blocked

Review objectives and instruction

AI help

Available only with source grounding, privacy limits, age controls, and measurement.

AI source context

Teen Numbers Are Ten and Some More · Number Sense · CCSS.MATH.CONTENT.K.NBT.A.1 · Teen Numbers

Evidence: local lesson AI-help metadata only; source-grounding, privacy, age-safety, and measurement hooks do not prove real model quality, production telemetry, child AI approval, or AI tutor production readiness

Production AI readiness not claimed

AI source context

Assessment shape

Local lesson assessment shape is complete.

Local shape only; production answer-attempt telemetry, live ownership/RLS evidence, mastery interpretation, release, and production readiness are not claimed here.

Objectives: 3
Activity: Prompt ready
Quiz items: 3 items, 3 answer keys, 3 explanations
Reward: Completion reward ready

Assessment progress stays manual: do not auto-advance through uncertain answers, failed writes, consent, media, payment, learner choice, or AI-assisted checks.

Learning-loop evidence: Content-map contract only; persistence and production learner-progress writes require route/API evidence.

Manual policy: assessment, media, consent, payment, learner choice, failed writes, and AI-uncertain help stay under learner control.

Prerequisite: Complete or review Subtracting Means Taking Some Away; Use with parent or guardian controls for child learners

AI guardrails

Privacy

Do not send raw child free text without consent
Use source excerpts and non-identifying progress state only
Asset is not registry-gated

Age safety

Apply junior audience controls before AI-help claims
Keep child learner AI paths behind guardian/product review evidence before readiness claims

Measurement

Log AI help usage by surface and asset slug
Evaluate answer quality against source-grounded rubric before production-readiness claims
Tie remediation prompts to completion, retry, or review outcomes

Local AI-help guardrails only; they do not prove guardian approval, production telemetry, model evaluation, release, deployment, or AI tutor production readiness.

Source and rights

Source path: koydo-app/scripts/curriculum-authoring
License: ai-generated-koydo
Attribution: Attribution decision needs owner review
AI provenance: claude-opus-4-8

Source review gates: attribution_missing

Local source evidence only; this does not prove publication rights, attribution approval, AI provenance clearance, release, deployment, or production readiness.

Route review

Current route: /library/junior/mathematics/en/lesson/teen-numbers-ten-and-some-more
Route source: Fallback route needs owner canonical review
Candidate route: /library/junior/mathematics/en/lesson/teen-numbers-ten-and-some-more

Local route evidence only; fallback candidates need owner-approved canonical route policy before route writes, production discoverability, or readiness claims.

Content gates: canonical_target_web_missing_uses_library_fallback

lessonslessonslesson objectivesmedia scenesdrillspractice setsquizzesfeedbackcharacterscitationsconcept mapsprogressresumereviewremediation

Teen Numbers Are Ten and Some More

with Lumi

Lumi stands at a sunny kitchen table covered with red strawberries, carefully placing ten strawberries into a big round bowl and lining up extra strawberries beside it, counting aloud with a big smile.

Identify that any teen number is made of ten ones and some extra ones.
Count out ten objects and name how many extra ones remain to make a teen number.
Match a teen number to a description that shows ten ones and some extra ones.

Key terms

teen number: A number from 11 to 19 made of ten and extras.
ten ones: A group of ten single items grouped together.
extra ones: The single items left over after making one ten.
place value: The idea that a digit's spot tells its meaning.

Ten and Some More

Every teen number is made of one full group of ten ones plus some extra ones beside it. For example, thirteen is ten ones and three more ones, and seventeen is ten ones and seven more ones. The ten is the hidden part that is easy to forget, but it is always there inside every teen number from eleven through nineteen.

The Ten Comes First

When we write a teen number with two digits, the ten always comes first and the extra ones come second. In 15, the 1 stands for one group of ten and the 5 stands for five extra ones. That is why 15 is fifteen, not fifty-one. Knowing that the ten leads helps you read and write teen numbers correctly.

Worked examples

Build the teen number for ten and three.

Count ten strawberries into the bowl.
Place 3 more strawberries beside the bowl.
Ten ones and three extra ones make thirteen.

Answer: 13

What teen number is 10 blocks and 5 blocks?

Start with one group of ten blocks.
Add five extra blocks beside it.
Ten ones plus five ones is fifteen.

Answer: 15

Hi! I am Lumi. Today we are going to learn about teen numbers — numbers like 11, 12, 13, all the way up to 19. Here is the big secret: every teen number has ten ones inside it, plus a few extra ones. Let's use strawberries! First, I count out ten strawberries and put them into the bowl — one, two, three … ten! Now I add some more beside the bowl. If I add 3 more, I have ten ones AND 3 more ones — that makes 13! Thirteen means: ten ones AND three more ones. Fourteen means ten ones and four more ones. Seventeen means ten ones and seven more ones. Every teen number works the same way — ten ones first, then a few extras beside them. Here is a hint: whenever you see a teen number, just ask yourself — how many extra ones are sitting next to the ten?

Activity

Drag strawberries into the bowl to make ten ones, then place the extra ones beside it to build the teen number shown.

Practice

Make the number 16 using ten ones and some extra ones.

Explain why 12 is ten ones and two more ones.

Common mistakes to avoid

A teen number is just the extra onesA teen number always includes the hidden ten, so 13 is ten ones and three ones, not only three ones.
Digits can be read backwardsThe ten always comes first, so 15 means ten and five, which is fifteen, never fifty-one.

Check your understanding

Mia has 10 blocks in a bag and 5 blocks on the table. What teen number does she have in all?

Which of these means the same as 14?

Leo says 13 is just three ones with nothing else. Is Leo right?

Recap

Every teen number from 11 to 19 is made of one group of ten ones plus some extra ones beside it. The ten always comes first, so 15 means ten ones and five extra ones, which we read as fifteen.

Reflect

When might it help to group ten things together before counting the extras?