Multiplying two negative numbers together: a real world example?

[One]

I was just thinking about this, I'm pretty good at maths but I'm stumped with this one. If you multiply a negative number by another negative number you get a positive number. I can't think of any real world examples where this can make sense. Now I'm thinking perhaps something at the cellular level and bacteria. I've no idea.

 

[Rich_L]

Number lines!

The main problem is in reality we don't tend to think of things in negative numbers too often in 'real life' but instead make up alternative things. I.e. on a North-South line you could describe it as going from say +10 North to -10 North but instead we say 10 South You don't have -£50 balance with someone you owe them £50 etc etc.

 

[[FnG]magnolia]

I'm trying to think of a blood types joke but ... nope, I'll come back to you.

 

[lrlcr]

couldn't think of a real solution so googled it:

here

Pretty rubbish, however the mathematical explanation makes the most sense. -1*-1 has to equal +1 or all of maths would break.

 

[[FnG]magnolia]

OP, are you happy now? YOU'VE BROKEN MATHS

 

[One]

couldn't think of a real solution so googled it:

here

Yup, debt works, that's a good enough real world example for me. Thanks.

Can anyone trump a financial example?

 

[steve-h]

well multiplying a negative number by -1 turns it positive... so there's a use.

 

[One]

well multiplying a negative number by -1 turns it positive... so there's a use.

Are you thick, ignorant, or trying to be funny? I can't tell.

 

[lrlcr]

I actually prefer the road and velocity explanation, however all of the examples are just semantics.

 

[One]

I actually prefer the road and velocity explanation, however all of the examples are just semantics.

...?

 

[RomanNose]

Wow you get mad easily, I wouldn't want to get in the way of your bacon.
I know one, it's to do with the force between two charges.
F = Qq/4πεr^2
Because if you have two of the same charges ( negative in some cases) you get a positive force indicating a repelling force. But it's all to do with convention, often you can flip signs around in sciences.

 

[Nitefly]

Pretty interesting point, but I feel OP is going to flip out when he discovers 1+1=window.

 

[One]

That's a pretty good one BigNose!

Actually you're wrong Nitefly, 1+1=2.

 

[touch]

I have 2 loans at £1000 each
Last year i had 3 loans at £1000 each, but i paid one off.


I have 1 less loan (-1) which was worth -£1000
Therefore the difference in my finances this year compared to last is: -1*-1000 (which is £1000 better off)

 

[Cleeecooo]

That's a pretty good one BigNose!

Actually you're wrong Nitefly, 1+1=2.

Everyone knows 1+1=window.

Are you thick, ignorant, or trying to be funny? I can't tell.

 

[Strife212]

If you multiply a negative number by another negative number you get a positive number. I can't think of any real world examples where this can make sense. I've no idea.

well multiplying a negative number by -1 turns it positive... so there's a use.

Are you thick, ignorant, or trying to be funny? I can't tell.

 

[One]

Everyone knows 1+1=window.

Are you thick, ignorant, or trying to be funny? I can't tell

What is wrong with you? Type 1+1 into a calculator. The answer is 2. How can you not know this? Window isn't even a number.

 

[RomanNose]

No they changed it, 1+1 used to equal two but because of political correctness ( we can't let children think that 2 parent famies are better than 1 parent families) we have to say window.

 

[One]

But the church doesn't accept window families so how can we be teaching kids this when it's not relevant yet? 1+1 still equals 2 until the church modernises.

 

[flibbage0]

It's like proving 0.9999 is = to 1.

1/3 =0.3333 so 3/3=0.9999

BUT 3/3 is 1.