Addressing Standard 7.NS.2

Apply and extend previous understandings of multiplication and division and of fractions to multiply and divide rational numbers.

Addressing Standard 7.RP

Analyze proportional relationships and use them to solve real-world and mathematical problems.

(Links to an external site.)Links to an external site.

Objectives

I can multiply a positive number with a negative number.

I can use rational numbers to represent speed and direction.

Online Workbook

Take me to the website.

Llévame al sitio web.

Lesson Summary

We can use signed numbers to represent the position of an object along a line. We pick a point to be the reference point, and call it zero. Positions to the right of zero are positive. Positions to the left of zero are negative.

When we combine speed with direction indicated by the sign of the number, it is called velocity. For example, if you are moving 5 meters per second to the right, then your velocity is +5 meters per second. If you are moving 5 meters per second to the left, then your velocity is -5 meters per second.

If you start at zero and move 5 meters per second for 10 seconds, you will be 5⋅10=50 meters to the right of zero. In other words, 5⋅10=50.

If you start at zero and move -5 meters per second for 10 seconds, you will be 5⋅10=50 meters to the left of zero. In other words,

- 5 \cdot 10 = - 50

In general, a negative number times a positive number is a negative number.