Math Help Forum

Math Help Forum Feed Site Feed

Go Back   Math Help Forum > Elementary and Middle School Math Help > Percents Fractions and Decimals
Reply
 
Thread Tools Display Modes
  #1  
Old 09-28-2008, 08:28 PM
Junior Member
 
Join Date: Sep 2008
Posts: 6
Country:
Thanks: 2
Thanked 0 Times in 0 Posts
zerbe is on a distinguished road
Default Finding Value of X division of fractions

I am trying to help my son out and I am drawing a blank on this problem.

x ÷ 7/8 = 3/5

I know I have to do something like this:
X x 8/7 = 3/5

I am having problems with the solutions because of the reduced 3/5. Others we could eye ball and find the solution, but this one I am having difficulty with. Regards.
Reply With Quote
Advertisement
 
  #2  
Old 09-28-2008, 09:19 PM
Jhevon's Avatar
meh...
 
Join Date: Feb 2007
Location: New York, USA
Posts: 10,378
Country:
Thanks: 1,964
Thanked 3,680 Times in 3,453 Posts
Jhevon has a reputation beyond reputeJhevon has a reputation beyond reputeJhevon has a reputation beyond reputeJhevon has a reputation beyond reputeJhevon has a reputation beyond reputeJhevon has a reputation beyond reputeJhevon has a reputation beyond reputeJhevon has a reputation beyond reputeJhevon has a reputation beyond reputeJhevon has a reputation beyond reputeJhevon has a reputation beyond repute
Default

Quote:
Originally Posted by zerbe View Post
I am trying to help my son out and I am drawing a blank on this problem.

x ÷ 7/8 = 3/5

I know I have to do something like this:
X x 8/7 = 3/5

I am having problems with the solutions because of the reduced 3/5. Others we could eye ball and find the solution, but this one I am having difficulty with. Regards.
now there are many ways to do this problem, a lot of room for creativity. but lets keep it simple.

we want to get x by itself. why waste time making the left hand side pretty. just get rid of the 7/8 right off the bat

x \div \frac 78 = \frac 35 .............multiply both sides by \frac 78 (do you see that this will cancel the 7/8 ?)

we get

x = \frac 35 \times \frac 78 ..............simplify

\Rightarrow x = \frac {3(7)}{5(8)} = \frac {21}{40}
__________________
<img src=http://www.mathhelpforum.com/math-help/image.php?type=sigpic&userid=3918&dateline=1208895702 border=0 alt= />

Join the dark side. We have cookies.

Reply With Quote
The following users thank Jhevon for this useful post:
Donate to MHF
  #3  
Old 09-29-2008, 11:56 AM
Junior Member
 
Join Date: Sep 2008
Posts: 6
Country:
Thanks: 2
Thanked 0 Times in 0 Posts
zerbe is on a distinguished road
Default

Thanks so much. I have a tendency to make these problems more difficult than they are.
Reply With Quote
  #4  
Old 09-29-2008, 12:02 PM
Jhevon's Avatar
meh...
 
Join Date: Feb 2007
Location: New York, USA
Posts: 10,378
Country:
Thanks: 1,964
Thanked 3,680 Times in 3,453 Posts
Jhevon has a reputation beyond reputeJhevon has a reputation beyond reputeJhevon has a reputation beyond reputeJhevon has a reputation beyond reputeJhevon has a reputation beyond reputeJhevon has a reputation beyond reputeJhevon has a reputation beyond reputeJhevon has a reputation beyond reputeJhevon has a reputation beyond reputeJhevon has a reputation beyond reputeJhevon has a reputation beyond repute
Default

Quote:
Originally Posted by zerbe View Post
Thanks so much. I have a tendency to make these problems more difficult than they are.
yes, the objective is to get x on one side by itself, and move everything to the other side. we move things by performing their opposite operation on both sides of the equation. so i wanted to move the 7/8 from the left. i noticed it was dividing, so i had to multiply both sides by 7/8. that way, the division cancels the multiplication on the left and i get rid of the 7/8 while at the same time, it ends up on the right, which is where i wanted to move it to
__________________
<img src=http://www.mathhelpforum.com/math-help/image.php?type=sigpic&userid=3918&dateline=1208895702 border=0 alt= />

Join the dark side. We have cookies.

Reply With Quote
  #5  
Old 10-16-2008, 02:28 PM
Junior Member
 
Join Date: Oct 2008
Location: Norfolk, england.
Posts: 10
Country:
Thanks: 0
Thanked 1 Time in 1 Post
SN1P3R is on a distinguished road
Default

There are two ways to do this, the guy above gave one, this is the other way:

your right with your 8/7, multiplying by this is the same as dividing by 7/8.

Thus you have x*8/7 = 3/5, this the same as 8x/7 = 3/5

so then we multiply both sides by 7 to get rid of it form the 8x

We do 3*7 which is 21

so we have 8x = 21/5

then simply divide both sides by 8, to get x = 21/5*8 which is 21/40.

I hope this helped, if you need any more help just PM me.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off
Forum Jump


All times are GMT -7. The time now is 02:27 PM.


Powered by vBulletin® Version 3.7.3
Copyright ©2000 - 2009, Jelsoft Enterprises Ltd.
SEO by vBSEO 3.2.0 ©2008, Crawlability, Inc.
©2005 - 2008 Math Help Forum


Math Help Forum is a community of maths forums with an emphasis on maths help in all levels of mathematics.
Register to post your math questions or just hang out and try some of our math games or visit the arcade.