What is a Number Line? :
What is a Number Line? Rulers are like a number line, except that they don’t have negative values.
Number lines usually show whole numbers and smaller units between the whole numbers. millimeters ¼ in. ½ in. 1/16 in. A number line has negative and positive values, and it has at least one unit of measure.
What are Negative Numbers used for? :
What are Negative Numbers used for? “Negative numbers” is a new concept this year. Negative numbers are used in a variety of ways that you learned about: Measuring temperatures: extremely low temperatures are recorded as negative numbers. A temperature of -40° is colder than -10°. Borrowing: Mary had 2 pencils in her desk on Monday. The next day, she lost both of them and borrowed 3 pencils from her friend. -2 -1 0 1 2 3 -3 Even though Mary got 3 pencils from her friend, she borrowed them and must return them. When you borrow something, you don’t own it, and you record what you borrow using negative numbers. -2 -3
Practice with Fraction and Decimal Equivalents :
Practice with Fraction and Decimal Equivalents …so that you can compare fractions and decimals and correctly place them on a number line. You know how to compare and order decimals: 21.99
22.01
22.08
22.10 You also know how to compare and order fractions: 7/8 > 4/8
5/6 > 2/3 (2/3 x 2/2 = 4/6)
6/2 > 7/3 And you know how to convert fractions and decimals: ½ = 0.5 0.3 = 3/10
¼ = 0.25 0.8 = 8/10 (4/5 simplified)
Understand Units of Measure :
Understand Units of Measure Before you can place a fraction or a decimal on a number line, you must first figure out the unit (or units) of measure on the number line. In the picture below, what are the units of measure? 1 2 3 4 5 6 7 8 Where would you place 2/16? Where would you place ¼? Where would you place 0.75?
Answers on the next page ? This number line begins at 0 and ends at 1. There are 8 larger unit marks and 16 smaller unit marks, including 8 smaller marks that “share” a spot with a larger mark. The black dot sits on the first large mark, and the red dot sits on the first small mark. Therefore, the black dot is at 1/8 of the length of this number line. The red dot is at 1/16 of the total length.
Slide 6:
Where would you place 2/16? Where would you place ¼? Where would you place 0.75? 2/16 can be located by using either the 16ths units, or the 8ths units because 2/16 can be simplified to 1/8.
The black dot is at 2/16. ¼ can be located by finding equivalent fractions whose denominator is in 8ths or 16ths:
¼ = 2/8 = 4/16
The blue dot is at ¼ 0.75 is equivalent to the fraction ¾, which can be converted to equivalent fractions whose denominator is in 8ths or 16ths.
0.75 = ¾ = 6/8 = 12/16
The yellow dot is at ¾ 0.75 2/16 1/4
Slide 7:
Where would you place 50 millimeters? 4 cm? 2.2 cm? 0.5 cm? Where would you place 1.5 inches? ¾ inch? 2.25 inches? 50mm = 5cm (yellow dot)
4cm (green dot)
2.2cm = 22mm (blue dot)
0.5cm = 5mm (red dot) 1.5 is halfway between 1 and 2 (yellow dot)
¾ greater than ½ and less than 1 (green dot)
2.25 is greater than 2, and 0.25 equals the fraction ¼ (blue dot) There are 10 millimeters in 1 centimeter More Practice…