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Directed numbers

I have taken to putting a small version of the table below in the top right of my PowerPoint slides and as an A3 poster on the (ink powered) whiteboards I use in many teaching rooms.

Students at level 2 doing algebra need to use these facts in most lessons, and seeing the rules all in one place seems to help.

I feel a YouTube coming on once I shift this cold…

A pair of directed numbers….

Adding and subtracting

Multiplying and dividing

Same signs

Add the numbers
The sign of the answer is the same as the sign of the numbers

The answer will be positive

Opposite signs

Find the difference of the numbers
The sign of the answer is the same as the sign of the largest number

The answer will be negative

This entry was posted on Thursday, February 22nd, 2007 at 22/02/07 and is filed under Maths. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

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