Pre-Algebra?

Question

Well, i'm in 7th grade and i'm in k-level math (for smart people). So that means I have to learn both 7th and 8th grade stuff. My teacher is really mean and she works really fast. We're learning intergers, decimals and fractions and i'm just not getting it. Any help please?

Ex:

-2.7 + 0.5 =

-1/2 + (-4/2) =

It wouldn't help me much if I did it on a calculator.

I'm not sure if I can whisk out a calculator when I'm taking a big test...

Answer 1

When working with decimals, just make sure the decimals are lined up and then add or subtract. In your example,
-2.7
0.5
--------
-2.2

I just subtracted the smaller number from the larger number and made sure my sign was correct (the negative number was larger, so the answer had to be negative).

-1/2 + (-4/2) is the same as -1/2 - 4/2. Since your denominator is the same, all you have to do is work with the numerators. -1 - 4 = -5. The answer is -5/2 or -2 1/2.

Hope that helped.

Answer 2

-2.7 + 0.5 =

I'll draw a number line because I think that that will help you visualize it:

<- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - >
-3.0 ' ' ' ' -2.5 ' ' ' ' -2.0 ' ' ' ' -1.5 ' ' ' ' -1.0 ' ' ' ' -.5 ' ' ' ' 0 ' ' ' ' 0.5

Okay, so we know that a negative number (will have a negative sign - in front of it) is less than zero and a positive number will NOT have a - in front of it.

Thinking about this, that means that negative numbers will continue to go to the LEFT and positive numbers will continue to go to the RIGHT:

< - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - >
NEGATIVE -------------- 0 ------------ POSITIVE

Think about it this way, the number 2 is two spaces away from zero in the RIGHT direction. -2 (negative 2), however, is two spaces away from zero to the LEFT.

If you are ADDING to a number, you are going in the positive direction, which we know is to the right. If we're subtracting a number, we go to the left.

Well anyway, let's get back to the question at hand.


-2.7 + 0.5 =

This means we start on the number line at -2.7
. . . . * (right here)
<- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - >
-3.0 ' ' ' ' -2.5 ' ' ' ' -2.0 ' ' ' ' -1.5 ' ' ' ' -1.0 ' ' ' ' -.5 ' ' ' ' 0 ' ' ' ' 0.5

and since we're ADDING 0.5, we move five spaces to the RIGHT of where -2.7 is located on the number line.
. * --> 1 ---> 2 ---> 3 ---> 4 ---> 5
<- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - >
-2.7 ' -2.6 ' -2.5 ' -2.4 ' -2.3 ' -2.2 ' -2.1

Okay, so we moved 5 spaces over in the POSITIVE direction, so we landed on -2.2. That means that -2.7 + 0.5 = 2.2

See if you can do the other one! Good luck!

Answer 3

I think what you need to remember is that numbers go to the infinitee in the negative and to the infinit to the positive with a zero smack dab in the middle.Try to imagine that in your mind.
Then...
.....-3.....-2.7.......-2.0.....-1..... 0 .....+1.....+2.....+3 etc....
The "-" brings us to the left and the "+" brings us to the right.
Standing on the negative 2.7 spot on this infinit number line which stretches off to the left of zero we are asked to take 0.5 steps in the positive direction and state where we are.
Then -2.7 + 0.5 = -2.2
The other one.......-1/2 +( -4/2) lets start with -4/2 we can see here that 4/2 is actually 2 so that gives us...-1/2 +(-2) and this brings us to -1/2 +(-2)= - 2 1/2
I hope this makes sence.It's kind of difficult doing math through writing.
In addition of negative numbers the numbers merely get bigger in the negative direction....(-5) + (-2)= -7
In subtracting negative numbers the number being subtracted has it's sign changed and the you just add..
(-5) - (-2) = (-5) - (+2)= - 3
There are a few other rules for multiplication but sounds like you will be getting there soon..they are not difficult.
Just practise and do lots of examples.
Hope this helps.

Answer 4

-2.2

-5/2 = 2.5
or
-0.5 - 2 = 2.5

You should be able to do these on the calculator.
I am not sure how to explain it.