# Maths problem

help me as my brain has gone to mush...

41 to 60 of 72 messages
mellifera    pirate
03/04/2008 at 14:04

TP - multiplication has a higher precedence than addition and subtraction. That measn you have to do it first. You must multiply 9 by 8 before you carry out the adds/subs.

when all the operators have the same precedence you do work from left to right.

and i'm wrong on MH I think - it's goes to 2/3 doesn't it?

03/04/2008 at 14:07
It doesn't work like that on Countdown .... obviously Carol doesn't know this either!  Best you explain it as I'm still a bit confused.
03/04/2008 at 14:09
mellifera speaketh a different tongue
03/04/2008 at 14:09
Is the answer 0.57 Melli, on the assumption no-one's born on 29th Feb?
Garr    pirate
03/04/2008 at 14:11
I'm going to hace a think about that when I get home Mellifera and come back here tonight probably with the wrong answer.
mellifera    pirate
03/04/2008 at 14:11

Yeah! that's right. BCDB

It's amazing I think

mellifera    pirate
03/04/2008 at 14:13
TP - I am right. On countdown they do the equivalent of what others on this thread did and break the procedure down into separate sums. That is, they use the answers of one sum to feed into the next.
Edited: 03/04/2008 at 14:17
03/04/2008 at 14:13

Whoooo-hooooooooooooooooo!

I was worried that I wouldn't get it right, and I'm a statistician by qualification. Especially since I struggled to get my head round teh switching problem before (it's a Bayesian thing, isn't it?)

mellifera    pirate
03/04/2008 at 14:15
Barkles - you are a headmaster aren't you? Haven't you ever heard of BODMAS?
mellifera    pirate
03/04/2008 at 14:16

Monty Hall is Bayesian.

congrats.

now help me out with the explanation of arithmetic

Edited: 03/04/2008 at 14:22
03/04/2008 at 14:18
Just doing brain test on Facebook, back in a tick ...
03/04/2008 at 14:20

Yes Melli I am, but if I knew what BODMAS meant I'd know if I knew it or not.

mellifera    pirate
03/04/2008 at 14:20

http://en.wikipedia.org/wiki/Order_of_operations

an example very like yours TP is given in the first few lines

(if you find wikipedia more credible than me)

mellifera    pirate
03/04/2008 at 14:22
Brackets, Orders, Division, Multiplication, Addition, Subtraction
03/04/2008 at 14:26

ah right.. yes.

erm....

Garr    pirate
03/04/2008 at 14:26
Nuts!  I'm struggling to get my formula correct for Mellifera's puzzle!  I've not given up yet.  I'll wait until I have a moment of inspiration, and if it doesn't come in the next 24 hours, I'll give in.  I've seen this problem before, but I just can't remember how to take everything into consideration.
03/04/2008 at 14:27

Mellifera i understand you!

Garr come on!

mellifera    pirate
03/04/2008 at 14:29

Garr - wanna hint?

03/04/2008 at 14:29

Precedence is just a way of avoiding ambiguity in an operation without brackets.

x+n*y ...  how do we know whether the person who wrote that operation means add xn to x then multiply by y; or do they mean multiply y by n then add to x. We know because of precedence. With no brackets we have to do the multiplication first, so it is "multiply n by y then add to x" that is meant.

If, conversely, what the person writing teh operation wants to express is "add n to x then multiply the whole thing by y" then they would have to write:

(x+n)*y ... the addition in the brackets has to be done *before* the multiplication, so we can override precedence with brackets.

Of course in the first example  we could express "multiply n by y then add to x" as:

x+(n*y) ... but the brackets are superfluous, because of the precedence of multiplication over addition. We already know we have to multiply first, so we don't need the brackets to tell us.

Next week, partial differential equations and hyperplanes. Remember to bring your sextants and plumb lines. I'm just off to get a new tank top.

mellifera    pirate
03/04/2008 at 14:30
don't try to take all the things that could happen into consideration, rather consider what couldn't happen.
41 to 60 of 72 messages