1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Help rearranging an equation

  1. Apr 17, 2009 #1
    i have to rearrange and equation

    without using the exact terms its along the lines of a = bcde and i have to make c the subject. have searched my study materiel and im fine with multiplications etc and doing the same to both sides when doing the rearrangement ie
    bcde = a
    bcde divided by b = a cancel the b to get cde = a over b (as in a fraction) but how do i write the next divisions ie
    cde/d = a over b cancel d to get ce = a over b but where do i put d? do i put a at the top and b and d below with a space between or do i have to write ce = a/b/d

    just cant get my head round it and google brought me to you guys

  2. jcsd
  3. Apr 18, 2009 #2


    User Avatar
    Science Advisor
    Homework Helper

    I will assume that none of b, d and e are zero, otherwise dividing by any of them would be a problem anyway.

    If you go back to
    bcde = a​
    instead of first dividing by b and then by d, you can of course divide by bd. That gives you
    bcde/(bd) = cde/d = bce/b = be = a/(bd).​
    On the other hand, as you had reasoned already, you can first divide by b and then by d, giving be = (a/b)/d.
    This shows that (a/b)/d = a / (b d).
    Writing it in fractions: you can put whatever you divide by below the bar:
    [tex]\frac{\frac{a}{b}}{d} = \frac{a}{b d}[/tex]

    Also note that (a / b) / d is something else than a / (b / d). When in doubt, you can plug in some numbers. Say a = 12, b = 6, d = 3. Then (a / b) / d = (12 / 6) / 3 = 2 / 3 while a / (b / d) = 12 / (6 / 3) = 12 / 2 = 6.
  4. Apr 19, 2009 #3
    [tex]\frac{\frac{a}{b}}{d} = \frac{a}{b d}[/tex]

    but does this not indicate a/bxd?

    i struggled with fractions 22 years ago at school and never thought id need to bother with them again and while i get what to do with everything else its how to write the equation correctly thats the problem as its on a computer test and if i put a space or symbol in the wrong place i dont get another chance
  5. Apr 19, 2009 #4


    User Avatar
    Science Advisor
    Homework Helper

    bd means b multiplied by d. It's also written as b d or b*d.
    Note that, when you type a/bxd into a computer, it will usually interpret it as (a/b)xd, i.e.
    [tex]\frac{a}{b} \times d[/tex]

    If you mean
    [tex]\frac{a}{b \times d}[/tex]
    you should write a/(bxd)
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Help rearranging equation Date
B Help rearranging. Jul 22, 2016
Help in rearranging a formulae Dec 28, 2013
Help needed, rearranging polynomial for inverse equation Mar 3, 2013
Help Me Rearrange May 19, 2011
Need help rearranging an equation Mar 11, 2009