Lesson · Grade 9 · Mathematics

Negative Fractions and Decimals on a Number Line

  • Grade 9
  • Mathematics
  • 2 min 10 s
  • British Columbia
  • BC9-MA-01

The video shows that −3/4, (−3)/4 and 3/(−4) are all the same number, −0.75, then writes −3/4, −2/3, −0.6 and 1/2 as decimals and marks them on a number line. It shows that −3/4 is smaller than −2/3 because it sits further left, which corrects the common mistake of thinking it is bigger because 3/4 is bigger than 2/3.

Concept: Rational numbers: fractions and decimals below zero

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In one sentence

The question this lesson answers

Which is smaller, negative three quarters or negative two thirds?

It is tempting to say negative two thirds, as three quarters is bigger than two thirds.

Transcript

What the lesson says

Which is smaller, negative three quarters or negative two thirds?

It is tempting to say negative two thirds, as three quarters is bigger than two thirds.

Both are rational numbers: they can be written as one integer over another, with a bottom that is not zero.

An integer is a whole number or its negative, like negative 3, 0 or 4.

The minus sign of a fraction can go in front, on the top, or on the bottom.

Each one equals negative 0.75: 3 divided by 4 is 0.75, and one minus sign makes it negative.

So all three are the same number.

To compare, write each as a decimal. Negative three quarters is negative 0.75.

2 divided by 3 is 0.666 and so on, so negative two thirds is about negative 0.67.

Add two more: negative 0.6, which is negative 6 tenths, and one half, which is 0.5.

On a number line, numbers get smaller to the left and bigger to the right.

Mark negative three quarters, negative two thirds, negative 0.6 and one half.

Negative 0.75 is further left than negative 0.67, so negative three quarters is smaller.

Three quarters is bigger than two thirds, so negative three quarters is further from zero.

Below zero, further from zero means further left, so smaller.

From smallest to biggest: negative three quarters, negative two thirds, negative 0.6, one half.

Further left on the number line means smaller, so negative three quarters is less than negative two thirds.

Curriculum

Where this fits

British Columbia, Grade 9

Mathematics, Number: operations with rational numbers (addition, subtraction, multiplication, division, and order of operations)BC9-MA-01

Next: Adding and Subtracting Negative Fractions and Decimals

The outcomes and strands follow the British Columbia curriculum.