Add multiples of 10
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Add multiples of 10: skill guide
| Objective | Learners will be able to add a multiple of 10 from 20 to 90 and a number from 1 to 9 by counting full ten strips as tens and the extra dots as ones. |
|---|---|
| Grade | Grade 1 |
| Standard | CCSS.MATH.CONTENT.1.NBT.C.4 |
| Difficulty | Developing · Mixed |
| Representation | Ten strip, Numerical equation |
| Practice format | Interactive, account-free practice with immediate feedback |
Objective
Learners will be able to add a multiple of 10 from 20 to 90 and a number from 1 to 9 by counting full ten strips as tens and the extra dots as ones.
What this practice covers
Each problem shows ten strips and an equation such as 40 + 3 or 3 + 40. The dots for the two numbers appear in two colors. Together they fill one strip for each ten, with the ones in the last strip. The learner finds the total and taps it from five choices. The tens number is from 20 to 90 and the other number is from 1 to 9, so sums run from 21 to 99. The tens number comes first in some problems and second in others.
Standards alignment
Supports Common Core: CCSS.MATH.CONTENT.1.NBT.C.4 — Add within 100 by combining a one-digit number and a multiple of 10.
Who it’s for
This practice is for Grade 1 learners who can count by tens and are learning how tens and ones make a two-digit number. It also suits older learners who still count every dot one by one.
What to know first
- Learners should count reliably, read two-digit numerals, and understand addition as joining parts. Each problem shows the sum on ten strips.
Difficulty and scaffolding
Developing · Mixed stage
Problem representations
- Ten strip
- Numerical equation
Three worked examples
- For 40 + 3, four strips are full and the next strip has 3 dots. Four tens and 3 ones make 43.
- For 6 + 70, seven strips are full and the next strip has 6 dots. Seven tens and 6 ones make 76.
- For 90 + 8, nine strips are full and the last strip has 8 dots. Nine tens and 8 ones make 98.
Likely misconceptions
- Learners may count every dot from one and lose count in the larger sums. Some mix up the tens and the ones when they write the number. Count the full strips by tens first, then count the dots in the last strip as ones.
Hints and explanations
- For 40 + 3, four strips are full and the next strip has 3 dots. Four tens and 3 ones make 43.
- For 6 + 70, seven strips are full and the next strip has 6 dots. Seven tens and 6 ones make 76.
- For 90 + 8, nine strips are full and the last strip has 8 dots. Nine tens and 8 ones make 98.
What to practice next
Next, Numerical sums with multiples of 10 asks for the same kind of sums with numerals only and no ten strips.
Editorial review
Reviewed by Brilliant’s curriculum team. Exercises are generated within defined difficulty ranges and checked against verified answer rules.
Add multiples of 10 FAQs
What is the goal of add multiples of 10?
The goal is to see a two-digit sum as tens and ones. A learner should be able to count the full strips by tens, add the extra dots as ones, and name the total without counting every dot.
Should this practice be timed?
No timer is required. First build accurate, understandable strategies. Speed usually improves as learners count strips by tens and see how the tens and ones are written as digits.
What should a learner do after a mistake?
After a wrong answer, the learner gets a second try. Count the full strips by tens, then count the dots in the last strip, and say the number. A short explanation helps more than a quick second 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 one.