HCPSS Curriculum Framework
Common Core Mathematics 6
Unit 2: The Number System
Overview (Big Ideas):
This unit focuses on completing understanding of division of fractions and extending the notion
of number to the system of rational numbers, which includes negative numbers. Students use the
meaning of fractions, the meanings of multiplication and division, and the relationship between
multiplication and division to understand and explain why the procedures for dividing fractions
make sense. Students use these operations to solve problems. Students extend their previous
understandings of number and the ordering of numbers to the full system of rational numbers,
which includes negative rational numbers, and in particular negative integers. They reason about
the order and absolute value of rational numbers and about the location of points in all four
quadrants of the coordinate plane. (adapted from CCSS Grade 6 page 39)
Enduring Understandings:
1. Rational numbers are a natural extension of the way that we use numbers.
2. Rational numbers are a set of numbers that includes whole numbers and integers as well as
numbers that can be written as the quotient of two integers, a divided by b, where b is not
zero.
3. Rational numbers allow us to solve problems that are not possible to solve with just whole
numbers or integers.
4. Rational numbers have multiple interpretations, and making sense of them depends on
identifying the unit.
o The concept of unit is fundamental to the interpretation of rational numbers.
o One interpretation of a rational number is as a part-whole relationship.
o One interpretation of a rational number is as a measure.
o One interpretation of a rational number is as a quotient.
o One interpretation of a rational number is as a ratio.
o One interpretation of a rational number is as an operator.
o Whole number conceptions of unit become more complex when extended to rational
numbers.
5. Any rational number can be expressed as a fraction in an infinite number of ways.
6. Between any two rational numbers there are infinitely many rational numbers.
7. A rational number can be expressed as a decimal.
8. The interpretation of the operations on rational numbers are essentially the same as those on
whole numbers, but some interpretations require adaptation, and the algorithms are different.
9. Estimation and mental math are more complex with rational numbers than with whole
numbers.
Source:
Barnett-Clarke, C., Fisher, W., Marks, R., & Ross, S. (2010). Developing essential
understanding of rational numbers for teaching mathematics in grades 3-5. Reston, VA:
The National Council of Teachers of Mathematics, Inc.
Howard County Public Schools Office of Secondary Mathematics Curricular Projects has licensed this product
under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.
Essential Questions:
o How does division of fractions relate to multiplication of fractions?
o How is division of fractions used in the real world?
o Why is the quotient greater than the divided when dividing by a value less than one?
o How does repeated subtraction or equal groups relate the measurement concept?
o How much is one as it relates to the partition concept?
o What is the difference between factors and multiples?
o What is the meaning of positive and negative numbers and zero in real-life situations?
o How and why are rational numbers ordered? How and why is absolute value ordered?
o What is the definition of coordinate plane terminology and where are the quadrants
located?
o What is the conceptual understanding of absolute value and in terms of a real-world
context?
Curriculum Standards:
6.NS.A Apply and extend previous understandings of multiplication and division to divide
fractions by fractions.
1. Interpret and compute quotients of fractions, and solve word problems involving
division of fractions by fractions, e.g., by using visual fraction models and equations to
represent the problem. For example, create a story context for (2 / 3)  (3 / 4) and use a
visual fraction model to show the quotient; use the relationship between multiplication
and division to explain that (2 / 3)  (3 / 4)  8 / 9 because 3 / 4 of 8 / 9 is 2 / 3 . (In
general, (a / b)  (c / d)  (ad) / (bc) .) How much chocolate will each person get if 3 people
share 1 / 2 lb of chocolate equally? How many 3 / 4 -cup servings are in a 2 / 3 of a cup of
yogurt? How wide is a rectangular strip of land with a length 3 / 4 mile and area 1 / 2
square mile?
6.NS.B Compute fluently with multi-digit numbers and find common factors and multiples.
2. Fluently divide multi-digit numbers using the standard algorithm.
3. Fluently add, subtract, multiply, and divide multi-digit decimals using the standard
algorithm for each operation.
4. Find the greatest common factor of two whole numbers less than or equal to 100 and
the least common multiple of two whole numbers less than or equal to 12. Use the
distributive property to express a sum of two whole numbers 1-100 with a common
factor as a multiple of a sum of two whole numbers with no common factor. For
example, express 36  8 as 4(9  2) .
6.NS.C Apply and extend previous understandings of numbers to the system of rational
numbers.
5. Understand that positive and negative numbers are used together to describe quantities
having opposite directions or values (e.g. temperature above/below zero, elevation
above/below sea level, credits/debits, positive/negative electric charge); use positive
and negative numbers to represent quantities in real-world contexts, explaining the
meaning of 0 in each situation.
Howard County Public Schools Office of Secondary Mathematics Curricular Projects has licensed this product
under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.
6. Understand a rational number as a point on the number line. Extend number line
diagrams and coordinate axes familiar from previous grades to represent points on the
line and in the plane with negative number coordinates.
a. Recognize opposite signs of numbers as indicating locations on opposite sides of
0 on the number line; recognize that the opposite of the opposite of a number is
the number itself, e.g., (3)  3 and that 0 is its own opposite.
b. Understand signs of numbers in ordered pairs as indicating locations in
quadrants of the coordinate plane; recognize that when two ordered pairs differ
only by signs, the locations of the points are related by reflections across one or
both axes.
c. Find and position integers and other rational numbers on a horizontal or vertical
number line diagram; find and position pairs of integers and other rational
number on a coordinate plane.
7. Understand ordering and absolute value of rational numbers.
a. Interpret statements of inequality as statements about the relative position of
two numbers on a number line diagram. For example, interpret 3  7 as a
statement that 3 is located to the right of 7 on a number line oriented from left
to right.
b. Write, interpret, and explain statements of order for rational numbers in realworld contexts. For example, write 3C  7C to express the fact that 3C is
warmer than 7C .
c. Understand the absolute value of a rational number as its distance from 0 on the
number line; interpret absolute value as magnitude for a positive or negative
quantity in a real-world situation. For example, for an account balance of -30
dollars, write 30  30 to describe the size of the debt in dollars.
d. Distinguish comparisons of absolute value from statements about order. For
example, recognize that an account balance less than -30 dollars represents a debt
greater than 30 dollars.
a. Solve real-world and mathematical problems by graphing points in all four
quadrants of the coordinate plane. Include use of coordinates and absolute
value to find distances between points with the same first coordinate or the
same second coordinate. Interpret division of a unit fraction by a non-zero whole
number and compute such quotients. For example, create a story context for (1/3) 
4, and use a visual fraction model to show the quotient. Use the relationship between
multiplication and division to explain that (1/3)  4 = 1/12 because (1/12)  4=1/3.
b. Interpret division of a whole number by a unit fraction, and compute such quotients.
For example, create a story context for 4  (1/5), and use a visual fraction model to
show the quotient. Use the relationship between multiplication and division to
explain that 4  (1/5) = 20 because 20  (1/5) = 4.
Common Misconceptions:
o Students may incorrectly model division of fractions.
o Students may interchange the uses for factors and multiples.
o Students may improperly place the decimal in an answer.
o Students may not understand that larger negative numbers are smaller in value.
o Students may confuse the absolute value symbol with the number one.
Howard County Public Schools Office of Secondary Mathematics Curricular Projects has licensed this product
under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.