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December 19th, 2008, 11:43 AM   #1
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Integers:

Ok so, i'm ok when it comes to integers i just need a little clarifying... Here's the following problems that no matter what i do i don't get the answer found in the book..

1. 43.3 -56.9=? "Ok so here i got 13.6, which is wrong because in the book it says it -13.6. What did i do wrong?"

2. 5/2 - 7/2 - (0.5) + (0.5) = ? " Ok, so i think the 0.5 cancels each other and then the remaining problems is 5/2 - 7/2, but the answer would
be -2/2, and the book says its zero. Why is that?"
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December 19th, 2008, 02:49 PM   #2
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Re: Integers:

Question: What do these have to do with "Integers"?

#1... If you can't see your way through this you REALLY need to get a tutor. If you subtract a larger number from a smaller it HAS to be a negative result.

#2... If you have stated the question properly, the book is wrong.
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January 2nd, 2009, 10:53 AM   #3
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Re: Integers:

Okay... This is my first post here on My Math Forum.

1) 43.3 - 56.9 = -13.6

When you subtract two numbers, one of which is positive, and the other negative, just subtract them as you would normally, that is, subtract the smaller number from the larger number, then put in the sign of the larger number.

In this case, the larger number is 56.9, and it has a negative sign before it, so put in a negative sign in your answer.

2) Yes, the -0.5 and + 0.5 cancel each other. That leaves you with 5/2 - 7/2 = -2/2. -2/2 = -1. If you've posted the question correctly, the book is wrong.

I hope that helps.

ILoveMaths07.
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January 7th, 2009, 07:21 AM   #4
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Quote:
Originally Posted by ILoveMaths07
When you subtract two numbers, one of which is positive, and the other negative . . .
That doesn't make sense. You don't "subtract two numbers"; you subtract one number (the subtrahend) from another number (the minuend). When using a calculator, just enter the expression and then "=". When subtracting manually using the method usually taught, you need to decide how to proceed as illustrated by the examples below.

Example: 56.9 - 43.3 = 13.6 (you know how to do this).
Example: 43.3 - 56.9 = -13.6 (the result has the opposite sign from the result in the previous example because the numbers on the left-hand side were swapped, making the second number larger).
Example: -56.9 - 43.3 = -100.2 (this result consists of a minus symbol followed by the sum of 56.9 and 43.3).
Example: -43.3 - 56.9 = -100.2 (same method as in previous example).
Example: -43.3 - (-56.9) = -43.3 + 56.9 = 56.9 - 43.3 = 13.6.
Example: -56.9 - (-43.3) = -56.9 + 43.3 = -(56.9 - 43.3) = -13.6.
Example: 43.3 - (-56.9) = 43.3 + 56.9 = 100.2.

Once you've done various examples, this becomes very straightforward.

Perhaps the second question was intended to be 5/2 - 7/2 + (0.5) + (0.5) = ? as that does work out as zero.
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