CCSS.Math.Content.7.NS.A.2d

Math7th GradeApply and extend previous understandings of operations with fractions to add, subtract, multiply, and divide rational numbers.

The standard

Convert a rational number to a decimal using long division; know that the decimal form of a rational number terminates in 0s or eventually repeats.

Common Core State Standards for Mathematics

What this standard means

Students need to use long division to turn fractions into decimals, including negative fractions. They should keep dividing until the decimal ends or until they notice a repeating pattern. They also need to explain why a decimal must either terminate or repeat, based on remainders.

Mastery looks like clean long division, correct decimal notation, and repeating bars placed over the right digits. Common trouble spots are stopping too soon, losing track of remainders, putting the repeating bar in the wrong place, and mishandling negative signs.

Ways to teach it

Have students use fraction cards like 3/8, 2/3, and 5/6, then sort their long-division results into terminating and repeating groups.
Ask students to write: How do remainders help you know when a decimal will repeat?
Give four fractions, 7/10, 1/6, 4/9, and -3/4, and ask students to convert each by long division.
Connect to money by comparing why 1/4 of a dollar is exact, but 1/3 of a dollar needs rounding.

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CCSS.Math.Content.8.NS.A
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CCSS.Math.Content.7.NS.A.2b
Understand that integers can be divided, provided that the divisor is not zero, and every quotient of integers (with non-zero divisor) is a rational number. If ...
CCSS.Math.Content.8.NS.A.1
Know that numbers that are not rational are called irrational. Understand informally that every number has a decimal expansion; for rational numbers show that t...