15.8-27.4=-11.6 every time I try to work it out I get -12.4, why?

Hi Chris,

I was coaching a student yesterday and I tought him this method of yours.

He seemed to think that it would work for him.  I had never thought of it that way before.

So thank you 

Although  when they first start learning addition and subtraction of directed numbers it is nice for them to understand the numberline and how it works properly

Can you try and show us your working so that we can help you see what you are doing wrong please.

Ignore the signs....take the "bigger' thing  and subtract the "smaller" thing....so we have

27.4 - 15.8  =  11.6

Now..ask yourself the question....what was the sign on the "bigger" thing.....a "negative," right??

Then...that's the sign we use for our answer....!!!  ( -11.6 )

This method always works when we have numbers with different signs......