Welcome to H3 Maths

Blog Support for Growing Mathematicians

Working with negative numbers – Part II

July31

– (-16) = +16

“How do you go from ‘ – (–16)’ to ‘ + 16‘ in your first step?” This is actually a fairly important concept and here’s a mental picture that I ran across in an algebra newsgroup:

Imagine that you’re cooking some kind of stew, but not on a stove. You control the temperature of the stew with magic cubes. These cubes come in two types: hot cubes and cold cubes.

If you add a hot cube (add a positive number), the temperature goes up. If you add a cold cube (add a negative number), the temperature goes down. If you remove a hot cube (subtract a positive number), the temperature goes down. And if you remove a cold cube (subtract a negative number), the temperature goes UP! That is, subtracting a negative is the same as adding a positive.

Now suppose you have some double cubes and some triple cubes. If you add three double-hot cubes (add three-times-positive-two), the temperature goes up by six. And if you remove two triple-cold cubes (subtract two-times-negative-three), you get the same result. That is, –2(–3) = + 6.

There’s another analogy that I’ve been seeing recently. Letting “good” be “positive” and “bad” be “negative”, you could say:

good things happen to good people: a good thing  (+) x (+) = +ve answer
good things happen to bad people: a bad thing  (+) x (-) = -ve answer
bad things happen to good people: a bad thing (-) x (+) = -ve answer
bad things happen to bad people: a good thing (-) x (-) = +ve answer

Full article here

by posted under Uncategorized | Comments Off on Working with negative numbers – Part II    

Comments are closed.

Post Support

NCEA Level 2 Algebra Problem. Using the information given, the shaded area = 9, that is:
y(y-8) = 9 –> y.y – 8y – 9 =0
–> (y-9)(y+1) = 0, therefore y = 9 (can’t have a distance of – 1 for the other solution for y)
Using the top and bottom of the rectangle,
x = (y-8)(y+2) = (9-8)(9+2) = 11
but, the left side = (x-4) = 11-4 = 7, but rhs = y+? = 9+?, which is greater than the value of the opp. side??
[I think that the left had side was a mistake and should have read (x+4)?]

H3 Viewers



Skip to toolbar