Mathematics
Grade 3
15 min
Benchmark fractions
Benchmark fractions
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1
Introduction & Learning Objectives
Learning Objectives
Identify the benchmark fractions 0, 1/2, and 1 on a number line.
Determine if a given fraction is less than, equal to, or greater than 1/2.
Compare two fractions by reasoning about their position relative to the benchmark of 1/2.
Compare two fractions with the same numerator or denominator by reasoning about their distance from the benchmarks 0 or 1.
Use the symbols <, >, and = to correctly record the results of fraction comparisons.
Explain their comparison strategy using the language of benchmark fractions.
Would you rather have 1/3 of a giant cookie or 5/6 of it? ๐ช Using special 'benchmark' fractions can help you choose the bigger piece every time!
In this lesson, you will learn about special, easy-to-picture fractions called benchmar...
2
Key Concepts & Vocabulary
TermDefinitionExample
Benchmark FractionA common, easy-to-understand fraction that you can use to measure or compare other fractions. The most important benchmarks for Grade 3 are 0, 1/2, and 1.To compare 4/10, you can think, 'I know 5/10 is 1/2, so 4/10 must be a little less than the benchmark 1/2.'
FractionA number that shows a part of a whole or a part of a group. It has a numerator (top) and a denominator (bottom).The fraction 3/4 means we have 3 parts out of a whole that is split into 4 equal parts.
NumeratorThe top number in a fraction. It tells you how many equal parts you have.In the fraction 5/8, the numerator is 5.
DenominatorThe bottom number in a fraction. It tells you how many equal parts the whole is divided into.In the fraction 5/8, the denominator is 8.
Equivalen...
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Core Formulas
The 'Compare to 1/2' Rule
For a fraction \frac{a}{b}: If a < (b รท 2), then \frac{a}{b} < \frac{1}{2}. If a > (b รท 2), then \frac{a}{b} > \frac{1}{2}. If a = (b รท 2), then \frac{a}{b} = \frac{1}{2}.
Use this rule to quickly check if a fraction is smaller or larger than one-half. First, find half of the denominator. Then, compare the numerator to that number.
The 'Distance from 1' Rule
To compare two fractions close to 1, like \frac{7}{8} and \frac{9}{10}, find the 'missing piece' for each. The fraction with the smaller missing piece is the larger fraction.
This is useful when both fractions are greater than 1/2. For 7/8, the missing piece is 1/8. For 9/10, the missing piece is 1/10. Since 1/10 is smaller than 1/8, 9/10 is closer to 1...
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Challenging
For which pair of fractions would using the benchmark 1/2 be the MOST helpful comparison strategy?
A.6/8 and 7/8
B.8/9 and 9/10
C.3/8 and 6/10
D.2/5 and 3/5
Challenging
I am a fraction. My denominator is 8. I am greater than 1/4 but less than 1/2. What fraction am I?
A.1/8
B.3/8
C.5/8
D.2/8
Challenging
Which comparison is correct for 4/7 and 5/9? Both fractions are greater than 1/2.
A.4/7 > 5/9 because 4/7 is further from 1/2.
B.5/9 > 4/7 because 9 is a bigger number than 7.
C.4/7 = 5/9 because they are both one piece more than half.
D.5/9 > 4/7 because 5/9 is closer to 1.
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