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05-04-2012   #2

Join Date: Dec 2011
Posts: 90

Quote:
 Originally Posted by seal123 i need help with mutiply, divived, add,& subturacting fraction. like if only have one number + a fraction what do we do. but we need to figure them out frist or something.
You might want to give an example about the 'figure them out first' part. I'm guessing that you mean changing the bottom denominator.

Adding fractions with different denominators can be done by making a common number for the denominators. For example:

4/9 + 2/3 = ?
We can't just add them together, because they have different denominators (bottom numbers). So, what we can do, is multiply one of the fractions, both at the top and bottom.

4/9 + (2*3)/(2*3) 'Here, you're multiplying the second fraction's top and bottom numbers.

4/9 + 6/9 = ?

Then, it makes it easier, as you can do it simply.

4/9 + 6/9 = 10/9 = 1 1/9.

Minusing fractions is similar:
2/5 - 6/20
= (2*4)/(5*4) - 6/20
= 12/20 - 6/20
= 6/20
= 3/10 (simplified)

----------------------------
Multiplying fractions is a lot different. Be careful in mixing them up!
To multiply fractions, you simply multiply the top, and multiply the bottom, and you're done.

7/9 * 4/7 = (7*4)/(9*7)
=28/63

Dividing is different from all other types. Instead, you inverse (rotate around) the second number. You must rotate the second number for it to work.

4/9 rotated around would be 9/4.

Then, once rotated, you can multiply.

10/12 divided by 5/2
= 10/12 * 2/5
= 20/60
= 3

Quote:
 Originally Posted by seal123 also how do we mutiply a huge number like 100003333*963452= how do times that. what it = a bigger number or a smaller number. but dose it get harder in a high school.
Well, in high school, you usually will be able to use a calculator, as it would be easier. You use a scientific calculator, which can allow bigger numbers, such as 10003333 to be multiplied.

However, right now, you would do it like normal multiplication. It's painful, I know

10003333
963452 *
20006666 +
500166650 +
.....
and so on.