Math Is Fun Forum

spoiled513

Member

Registered: 2010-01-02

Posts: 4

i need help!

okay, so long story short im going back to school to get my diploma. they send me books.. i read them... i take the 20 ?'s exams.... done. okay.
well im great at math.. really its my best subject (which im sure has now made me look dumb lol) well im doing fractions and i cant seem to remember how to find the sum.
example: whats the sum of 2/5 and 2/4
how do i figure this out. im sure its in my book but i cant seem to find it. im not looking for an answer to all my exam questions... just help to show me how to do it.
hope someone can help soon!
Thanks ahead of time

Fruityloop

Member

Registered: 2009-05-18

Posts: 143

Re: i need help!

You need to find the lowest common multiple of 5 and 4 (called the LCM), and then convert the fractions into that number in the denominator so you can add them.
Fruityloop

spoiled513

Member

Registered: 2010-01-02

Posts: 4

Re: i need help!

thanks!!! i used to be so good at this fraction stuff and now im getting cought up every other question! and after 11 ppl reading this .. you finally answerd.. so thanks! really apprciate it!! now i have to find out how to do products with wholes and fractions. like 3 2/3 and 14 2/5 .... erg this drags! i cant believe how stupid i have become!

Fruityloop

Member

Registered: 2009-05-18

Posts: 143

Re: i need help!

Don't feel bad.  The only way to stay good at math is to practice doing problems.  If you're aren't doing it, then you will have a tendency to forget.  I think it's that way with pretty much everyone.
With whole numbers you multiply the denominator by the whole number part and add it to the numerator.
So 3 2/3 = 11/3

Fruityloop

Last edited by Fruityloop (2010-01-02 19:03:22)

Identity

Member

Registered: 2007-04-18

Posts: 934

Re: i need help!

First you must convert them to improper fractions:

Let a,b, and c be numbers. Then

So

and

Then you multiply the tops and bottoms of the improper fractions:

We can cancel a 3 from the top and bottom:

spoiled513

Member

Registered: 2010-01-02

Posts: 4

Re: i need help!

oh i agree 100%!! and your the absolute best! thank you so much for your help! its hard to call my friends at 2am lol. they might beat me! thanks again for all your help!

spoiled513

Member

Registered: 2010-01-02

Posts: 4

Re: i need help!

identity:
thanks! im still kinda confussed. i mean that makes since to me now and i can work out the problem taht way, but it isnt one of my answers on this review. it says
"..."
what is the product of 3 2/3  and  14 2/5
a) 52 4/15
b) 54
c)52 4/5
d) 42 4/5

i dont understand how to make them whole... do i multiply the whole numbers  then the fractions? this is so darn confussing nowwa days.

Fruityloop

Member

Registered: 2009-05-18

Posts: 143

Re: i need help!

Try thinking about it like this...
If you have 264/5 then you have 264 fifths correct?
OK.  So every 5 of those 264 fifths you can make a whole number correct?
This should lead you on the right path...

Last edited by Fruityloop (2010-01-02 19:33:52)