With all of the rules and scenarios,
remembering how to add and subtract
negative numbers can be difficult.
Here's a little trick to help you
remember. Let's say we want to solve
3 plus -7. First, imagine a
number line with a bird sitting on our
first number, 3. The operation plus or
minus tells you which end of the number
line to look at. Since we're adding, our
little bird will look right toward the
positive end. Our second number tells us
how far to move and which direction to
move. We'll move forward if it's positive
and backwards if it's negative. Since our
second number is a -7, our little
bird is going to move backwards seven
spaces. Since he landed at -4,
that's our answer: 3 plus -7
equals -4.
Let's try another one. What about
-2 minus -4? Our first
number is -2, so that's where
we'll start. Our operation is a minus, so
our bird will look left towards the
negative end. Our second number is a
-4; therefore, our bird will move
backwards 4 spaces. Our bird landed
at +2, and that's our answer:
-2 minus -4 equals 2.
Let's recap. The first number is where
you start. The operation tells you where
to look:
Plus, right, or minus, left. The second
number tells you how far to move and in
which direction: positive, forward, or
negative, backwards. Where you land is
your answer.
That's it! You now know a trick for
adding and subtracting negative numbers.