4th Grade · Number & Operations - Fractions
4.NF.C.5: Turn tenths into hundredths to add them, like 3/10 + 4/100
4.NF.C.5 is a 4th grade Common Core math standard in Number & Operations - Fractions. Here’s what it really covers, and how you can help your students learn it.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
The standard
Express a fraction with denominator 10 as an equivalent fraction with denominator 100, and use this technique to add two fractions with respective denominators 10 and 100. For example, express 3/10 as 30/100, and add 3/10 + 4/100 = 34/100.
In plain words
Turn tenths into hundredths to add them, like 3/10 + 4/100.
Sample questions from student practice
These questions from Bobby's Math Club are the kinds of questions your students will see. You can try answering them to see what a student might see.
Question 1 of 3
How many hundredths make the same amount as 1/10?
- 1
- 10
- 100
Where students can get stuck
- Adding tops and bottoms straight across, writing 3/10 + 4/100 = 7/110, without first renaming the tenths as hundredths.
- Renaming 3/10 as 3/100, changing the bottom to 100 but not multiplying the top by 10.
- Thinking 4/100 is larger than 3/10 because both of its numbers are bigger, not seeing that hundredths are tiny pieces.
Effective teaching strategies
- Shade 3 columns of a 10 by 10 grid and have students count the hundredths, so they see that 3/10 equals 30/100.
- Ask students to rename 3/10 as 30/100 by multiplying the top and bottom by 10, and only then add 4/100.
- Have students shade 3/10 and 4/100 on separate grids and say which covers more, and why a bigger bottom number means smaller pieces.
Units that teach this standard
Find where 4.NF.C.5 lands in the program you teach. Each unit has a guide written for families. Unit names and order vary between editions and districts, so your school’s own materials have the exact sequence.
Bridges in Mathematics
enVision Mathematics
Eureka Math
i-Ready Classroom Mathematics
Illustrative Mathematics
Math Expressions
Reveal Math
Zearn Math
Don’t see your curriculum? Contact Bobby and we’ll see if we can help!
Share it with families
Families can read Adding tenths and hundredths together for a plain-language look at this skill, with three questions to try together and ideas for helping at home.
Help every student practice fractions at home
In Bobby's Math Club, students practice at just the right level, with a hint when they need one, a clear explanation after every question, and kid-friendly videos. Unlimited practice is free for every family.
See how it works for teachers
Written by Robert “Bobby” Barnett
Bobby is an award-winning math teacher, the author of Meet Every Learner’s Needs, and the father of two elementary-school math learners. He uses Bobby’s Math Club with his own kids a few times every week. Learn more or contact Bobby.