I understand that a negative times a negative equals a positive, are there any real world examples of this?
I know if I have 3 jars with 5 cookies each that’s 15 cookies
3×5=15
What about (-3) x (-5) = +15
How is that expressed in a simple scenario like above?
In:
This property of negative numbers is useful all the time in engineering & physics.
Imagine you’ve got a road, and the road has a gradient. If the road is going uphill, the gradient is positive, if the road is going downhill then the gradient is negative.
Now also imagine you’ve got a car on this road, and you know the car’s velocity. Positive velocity means the car is going forward, negative velocity means the car is reversing. I want to work out how quickly the car is ascending or descending. I can find this out by multiplying gradient by velocity.
If the slope is going downhill (-ve) and the car is reversing back up it (-ve), then the car is actually going uphill and the ascent rate is positive.
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