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philreddy1985philreddy1985 Registered Posts: 23

I'm wondering if someone could please offer me some assistance when working out interpolation equations.

10% + 5510/14080 x 10 = 13.9 - 14 %

I just cant seem to get 13.9% or 14% when I work this out with a calculator. is there something I am missing out or am I just not working it out correctly?

Any help or assistance will be greatly appreciated


  • fournaanjezfournaanjez Registered Posts: 32
    edited June 2017
    Looks like it works to me, maybe its the order of calculations throwing you off.

    Division and multiplication first:
    (5510/14080) = 0.39134
    0.39134 x 10 = 3.9 (to 1 d.p)
    Followed by addition:
    10+3.9= 13.9% or 14% rounded up

    Hope this helps.
  • philreddy1985philreddy1985 Registered Posts: 23
    Thank you. But please can I ask how you are meant to know the order of those equations when in the textbook you are shown a formula to follow? Is there an easier way to reach this conclusion? I am finding this most confusing, nowhere in my AAT textbook is the equation explained the way you have explained above.

    Many thanks :)
  • IrrorateIrrorate Registered Posts: 139
    All mathematical calculations follow the rules of BODMAS/BIDMAS which determines the order in which to solve the equation.

    Order / Index
  • fournaanjezfournaanjez Registered Posts: 32
    Not sure if this is what you're asking (so please correct me if its not!) but when doing any equation, you need to follow it through in the same order.

    That order being:

    or BIDMAS/BODMAS is a good way to remember it.
  • fournaanjezfournaanjez Registered Posts: 32
    @Irrorate beat me to it...
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