Here is a list of fractions.  Take a guess which number they are closest to 0 , 1/2, or 1. Then move your mouse over the number to see if you are right.  If your mouse fails, check your guess with a calculator.

Look at each subtraction, problem take a guess on it's answer then move your mouse over the problem to find out how close you were.

1 5/8 - 7/15 =

32 10/11 - 99/100 =

59 1/3 - 42 7/8 =

1

In real life, often being able to get a reasonable estimate is more important than getting the actual answer.   A fraction capable calculator will give you the exact answer (assuming you enter the problem correctly), but if you don't have a "feel" for what the answer should be you can end up looking foolish if the data is entered incorrectly, and you do not catch it.

For example, a student recently took 3/8 - 1/2   and got  7/8, and didn't think anything of it. The student pressed the (+)sign instead of the (-) sign on the calculator. (real answer is -1/8)

Be sure to practice your estimating skills.

This brings us now to ACTUAL subtraction of fractions by hand.

It may have been a while since you have done this.  So here are a few tips to remember:

1. When the denominators (bottom numbers) are the same, DO NOT subtract THEM!  Just subtract the numerators, (top numbers)
   EX: 4/5 - 3/5  = 1/5
   
2. Always reduce your answers:
   EX: 3/6 is really 1/2 so call it that.
   EX: 13/8 is improper. That means the top is bigger than the bottom, and that is uncool most of the time, people don't say, "I have 13/8 pizzas. You reduce it by dividing and say, "I have 1 5/8 pizzas."
   
   
3. Remember if the denominators are DIFFERENT, you need to find a COMMON DENOMINATOR and corresponding numerators before you can subtract.
   EX: 3/4 - 2/5 = (multiplying the denominators will always give a common denominator)
   4 x 5 = 20; so I must find the corresponding numerators that will match the denominator of 20.
   3/4 x 5/5 = 15/20 and
   2/5 x 4/4 = 8/20...............so these two are what we subtract getting : 
   15 - 8 = 7
   20   20  20

Now comes the ALGEBRA:

Let's play a game of I'M THINKING OF A NUMBER.

Here is how it works:         I'll tell you a hint about the number I have in my mind. Then you do some mental calculation, or use a piece of paper to undo my hint  and reveal  my number. When you think you know the answer, just click on the answer button to check it.

HERE TRY A SAMPLE!

NOW LET'S TRY SEVERAL SOLO!
Be sure not to click on the answer until you figure it out yourself.

I'm thinking of a big number,  If I add 3/8, I will  have 512 and 3/5.  What is my number?	answer
I'm thinking of a small number.   If I add 1/3, I will  have 3/4.  What is my number?	answer
I have a number in my mind.  Now if I add 4 and then add 5/6 more, I will  have 32 and 1/2.  So what number is in my mind?	answer
Hello.  I have a number locked in my car glove compartment.   If you are smart enough to figure it out, I'll give you this number in dollar bills. Give it a try. If we add7/8 to this number and then add 1/3 more we will end up with 29/24.   What is my number?	answer
Well howdy, I've got another number in ma head.   If I take add 17,  and then add 3/5 more, well by George, I'll get 100.   Can you tell me my number?	answer

ANSWERS:

SAMPLE: The answer here is 27 and 1/2. If I start at 28 and REMOVE the 1/2 that I added, then I will be back at the original number, 27 1/2.

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no.1
The answer is 512 and 9/40.

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no.2
The answer is 5/12.

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no3.
the answer is 27 and 2/3.  You had to borrow on this one.
32 1/2 - 4 - 5/6

If I subtract the first two I get 28 1/2.

Then I subtract the last number from this: 28 1/2 - 5/6 or

28 3/6 - 5/6  (rewriting with the common denominator )

We can't take 5/6 away from the 3/6, so we borrow one from the 28 and turn it into 6/6.

Then we add these extra sixths to the 3/6 so we can subtract.

It now looks like this:

27 9/6 - 5/6 = 27 and 4/6 which reduces to 27 and 2/3.

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no4.
The answer is ZERO dollars for you!

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no 5.
The answer is 82 and 2/5.   WAY TO GO if you got this one right!!

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