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Compare Fractions Using Benchmarks and Number Lines

Students use benchmark fractions (0, 1/2, 1) and number lines to reason about the relative size of two fractions with different numerators and denominators. They develop number sense about fraction magnitude without always computing common denominators.

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Compare Fractions Using Benchmarks and Number Lines

Grade 4 · Comparing Fractions · question 1 of 3

0 of 20

20 rungs. A star at the top.

Which compares 1/2 and 1/10 correctly?

How it is taught

0:00 of 4:50

Benchmarks like 0, 1/2, and 1 help place fractions.

A fraction near 0 has a small top.

The number line shows which is closest.

Read it: Hold each fraction against a half

Which is more, 2/3 or 3/8? 2 is more than half of 3, and 3 is less than half of 8, so 2/3 is the greater fraction.

  1. Pick a benchmark both fractions are near: 1/2 or 1 whole.
  2. Decide if each fraction is more or less than the benchmark.
  3. The one above the benchmark is greater. Write the sign with its open side toward it.

A fraction is more than 1/2 when its top number is more than half of its bottom number.

If one fraction is above the benchmark and the other below, the benchmark sits between them.

Then no common denominator is needed to tell which is greater.

Compare each fraction with 1/2 or 1. The benchmark decides which is greater.

Calling 3/8 greater because 8 is a bigger number than 3.

Eighths are smaller pieces than thirds. 3/8 is less than 1/2 and 2/3 is more, so 2/3 is greater.

4/9 ___ 5/6 — <. 5/6 is more than 1/2 and 4/9 is less, so 4/9 < 5/6.

3/8 vs 4/6

Which is bigger — three eighths or four sixths? Let's use benchmarks to find out.

Our benchmarks are zero, one-half, and one. Every fraction lives somewhere on this line.

First, three eighths. Half of eight is four — so four eighths is one-half.

Three is less than four, so three eighths is less than one-half.

We drop three eighths to the left of one-half.

Now four sixths. Half of six is three — so three sixths is one-half.

Four is greater than three, so four sixths is greater than one-half.

Which is bigger?38vs46011248 = 123 < 4, so 38 < 123836 = 124 > 3, so 46 > 124638 < 46BIGGER46above 12
Grade 4 · Use 0, ½, and 1 to compare

We drop four sixths to the right of one-half.

Three eighths is below one-half and four sixths is above. Four sixths is bigger!

What you see

While they climb, your page writes one true line to ask about tonight, and a short note each Sunday.

MayaGrade 3 · Mathematics
Did you know?

A chessboard has 64 squares — share them out between the 8 rows and each row holds exactly 8.

Today’s goal
1 star — one skill mastered, every rung of its ladder climbed
Climbing now
Divide within 100

An example student.

MayaGrade 3 · Mathematics

Maya earned 2 stars this week — Interpret multiplication as equal groups, which took 6 answers over 3 days before its star landed 3 days ago and Multiply by 6, 7, 8 and 9. Next up: Divide within 100.

An example week.

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