TOPIC 9 · GRADE 4 BRIDGE
Common Denominators and Unlike Parts
Rename unlike pieces before combining them, beginning with tenths and hundredths.
MA.4.FR.2.3 · Grade 5 enrichmentBIG IDEA
Fractions can be added only after the pieces use a common unit. Equivalent fractions rename both amounts with the same denominator.
LEARN IT WITH A STORY
Rename juice portions with one cup scale
Tenths and hundredths cannot be counted together until their pieces have the same name. Three tenths becomes thirty hundredths, so 3/10 + 25/100 = 55/100.
- 1Find a denominator that both original denominators can make.
- 2Use equivalent fractions to rename each amount with that denominator.
- 3Combine the now-equal-size parts and check the result against 0, 1/2, and 1.
Rename 1/2 and 1/5 as tenths, then find their sum with a 10-part bar.
FRACTION WORD BANK
Tap a word, then turn the card
Say the word aloud before revealing its meaning. Tap again to return to the word.
WATCH AND NOTICE
Finding common denominators | Khan Academy
Pause when a model appears. Name the whole, denominator, numerator, and fraction before the teacher explains it.
Open on YouTube ↗WHAT TO KNOW
- In Grade 4, 3/10 becomes 30/100 so it can combine with hundredths.
- A common denominator is a shared piece size, often found with common multiples.
- For 1/2 + 1/3, sixths work: 3/6 + 2/6 = 5/6.
WATCH OUT
Adding tops and bottoms separately changes the piece size and is not valid.
TRY IT
Overlay fraction grids to find a shared partition before adding.