Taking away 10
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Taking away 10: skill guide
| Objective | Learners take 10 away from a two-digit number by removing one ten and keeping the ones. |
|---|---|
| Grade | Grade 1 |
| Standard | CCSS.MATH.CONTENT.1.NBT.C.5 |
| Difficulty | Developing · Mixed |
| Representation | Ten strip, Numerals |
| Practice format | Interactive, account-free practice with immediate feedback |
Objective
Learners take 10 away from a two-digit number by removing one ten and keeping the ones.
What this practice covers
Each problem shows a number from 21 to 99 as dots in ten strips, with an equation such as 58 − 10 = □. The ones digit is never 0, so the last strip is always partly filled. The learner takes away 10 and chooses how many remain. The answer has one fewer ten and the same ones digit. After the learner answers, the 10 dots that were taken away fade.
Standards alignment
Supports Common Core: CCSS.MATH.CONTENT.1.NBT.C.5 — Given a two-digit number, mentally find 10 more or 10 less.
Who it’s for
This practice is designed for Grade 1 learners working with tens and ones in two-digit numbers. It is also useful for older learners who want a quick visual review of what happens when 10 is taken away.
What to know first
- Learners should read two-digit numerals, know that a two-digit number is made of tens and ones, and understand subtraction as taking away and finding what remains.
Difficulty and scaffolding
Developing · Mixed stage
Problem representations
- Ten strip
- Numerals
Three worked examples
- 47 − 10 = 37: 47 is 4 full strips and 7 more dots. After taking away 10, 3 full strips and 7 dots remain.
- 93 − 10 = 83: 9 tens become 8 tens, and the 3 ones stay the same.
- 21 − 10 = 11: 2 tens become 1 ten, and the 1 one stays the same.
Likely misconceptions
- Learners may take away 1 instead of 10, as in 47 − 10 = 46, or count back 10 ones and lose track. Read the number as tens and ones, take away one ten, and check that the ones digit stays the same.
Hints and explanations
- 47 − 10 = 37: 47 is 4 full strips and 7 more dots. After taking away 10, 3 full strips and 7 dots remain.
- 93 − 10 = 83: 9 tens become 8 tens, and the 3 ones stay the same.
- 21 − 10 = 11: 2 tens become 1 ten, and the 1 one stays the same.
What to practice next
Next, finish number patterns that count down by 10, where each number has one fewer ten than the one before it.
Editorial review
Reviewed by Brilliant’s curriculum team. Exercises are generated within defined difficulty ranges and checked against verified answer rules.
Taking away 10 FAQs
What is the goal of taking away 10?
The goal is to see that taking away 10 leaves one fewer ten and the same ones. A learner should be able to find the answer without counting back 10 ones.
Should this practice be timed?
No timer is required. First build accurate, understandable strategies. Speed usually improves naturally as learners recognize groups of ten, familiar facts, and repeated patterns.
What should a learner do after a mistake?
Name the tens and ones in the first number, take away one ten, and check that the ones digit did not change. A short explanation is more valuable than immediately repeating the same guess.
How many problems should be completed at once?
A Quick check has 5 problems and a Practice session has 15. A learner may pause when attention drops. A short, successful session with clear reasoning is more useful than rushing through a longer set.