Ten More, Ten Less — Mental Math With Two-Digit Numbers
Find 10 more or 10 less than a two-digit number — all in your head. Look at the tens: only the tens digit changes, so there is no counting. Tap the number you think is right, and take all the time you need. A calm way to build place-value sense and mental math, aligned to Common Core 1.NBT.C.5 — mentally finding 10 more or 10 less than a two-digit number without having to count.
Find 10 more or 10 less than a two-digit number — all in your head. Look at the tens: only the tens digit changes, so there is no counting. Tap the number you think is right, and take all the time you need. A calm way to build place-value sense and mental math, aligned to Common Core 1.NBT.C.5 — mentally finding 10 more or 10 less than a two-digit number without having to count.
About this activity
This free, interactive place-value activity helps children see how our number system is built around groups of ten, using numbers up to . It runs in any modern browser — on a tablet, a phone, or the classroom whiteboard — with nothing to download.
It is aligned to Common Core 1.NBT.C.5 in the Number & Operations in Base Ten strand. Children work at their own pace with warm, instant feedback, and there is no timer or score to rush them.
What's inside this activity
- Designed for Grade 1 learners (ages about 5 to 9)
- Common Core strand: Number & Operations in Base Ten
- Aligned to Common Core standard 1.NBT.C.5
How to play
Children read the prompt and look at the ten-frames or blocks on the screen.
They fill, build, or choose to match the number being asked for.
A gentle check confirms a correct answer and invites another try when needed — calm, low-pressure practice throughout.
What your child practices
- Seeing a two-digit number as a group of tens plus some extra ones
- Building numbers up to from tens and ones
- Reading and writing numbers and connecting them to a picture of the quantity
- Noticing the patterns that make bigger numbers easier to understand
Learning goals
Understand a teen or two-digit number as some tens and some ones.
Compose and read numbers up to with confidence — the heart of Common Core 1.NBT.C.5.
Lay the base-ten foundation that multi-digit addition and subtraction depend on.
Frequently asked questions
- What does the Ten More, Ten Less — Mental Math With Two-Digit Numbers activity teach?
- Ten More, Ten Less — Mental Math With Two-Digit Numbers is a free interactive activity for Grade 1, focused on Number & Operations in Base Ten. Children play it right in the browser — no printing, login, or setup required.
- Is Ten More, Ten Less — Mental Math With Two-Digit Numbers free to use?
- Yes. Ten More, Ten Less — Mental Math With Two-Digit Numbers is completely free, with no signup and no paywall, on any tablet, laptop, or classroom whiteboard.
- Which ages is this activity for?
- It is designed for Grade 1 (Number & Operations in Base Ten) and works well for whole-class, small-group, or independent practice.
Practice this standard
See all 1.NBT.C.5 activitiesMore activities to try
- K.NBT.A.1Teen Numbers 11 to 19 — Double Ten Frame Activity
- 1.NBT.B.3Compare Two-Digit Numbers — Greater Than, Less Than, Equal
- 2.NBT.A.3Three Ways to Show a Number
- 1.G.A.3Equal Halves and Fourths — Find the Fair Shares | Grade 1 Geometry
- RF.1.3Build Blend and Digraph Words
- RF.1.3Add the Magic e — Long Vowel Words