Interesting maths problem
 Rorschach
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 Joined: 02 Jun 2008, 12:43
 Location: The north side of my town faces east, and the east faces south
Interesting maths problem
Try not to give it away too easily if you get it. It had me confounded for a good few minutes!
230  220 x 0.5 = ?
You may not believe it, but the answer really is 5!
230  220 x 0.5 = ?
You may not believe it, but the answer really is 5!
Bugger off.
 Deebank
 Resonator
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 Joined: 10 Oct 2003, 13:47
 Location: Ina beautiful place out in the country
Re: Interesting maths problem
Rorschach wrote:Try not to give it away too easily if you get it. It had me confounded for a good few minutes!
230  220 x 0.5 = ?
You may not believe it, but the answer really is 5!
Surely the most obvious answer? The one that immediately sprang to mind.
Why wouldn't I believe it?
I've been talking about writing a book  25 years of TEFL  for a few years now. I've got it in me.
Paid anghofio fod dy galon yn y chwyldro
Paid anghofio fod dy galon yn y chwyldro
 OUTPLAY
 hounds people off the board
 Posts: 19924
 Joined: 24 Apr 2007, 23:21
Re: Interesting maths problem
Yeah, it's obvious
230 minus 220 is 10
times that by 0.5 (i.e. half it), and you get 5
230 minus 220 is 10
times that by 0.5 (i.e. half it), and you get 5
GoogaMooga wrote:I don't know who it is that is throwing plastic bags overboard from ships, but it certainly isn't me, and I've never met anyone who does that.

 Posts: 2013
 Joined: 05 Jul 2017, 23:05
Re: Interesting maths problem
Surely one has to apply BIDMAS or whatever you call it, so you have
220 x .0.5 = 110.
Then
230  110 = 120.
If the answer really is 5 there's some other trick.
220 x .0.5 = 110.
Then
230  110 = 120.
If the answer really is 5 there's some other trick.
 souphound
 World Class Ignoramus
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Re: Interesting maths problem
Positive Passion wrote:Surely one has to apply BIDMAS or whatever you call it, so you have
220 x .0.5 = 110.
Then
230  110 = 120.
If the answer really is 5 there's some other trick.
That's the way I see it.
Footy wrote:Last week, I discovered that the cordless drill I bought about 5 years ago is, in fact, a cordless screwdiver.
 The Fish
 Beer Battered
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 Location: Hove Actually
Re: Interesting maths problem
Positive Passion wrote:Surely one has to apply BIDMAS or whatever you call it, so you have
220 x .0.5 = 110.
Then
230  110 = 120.
If the answer really is 5 there's some other trick.
That was my thought.
We're way past rhubarb
 Rorschach
 Posts: 3745
 Joined: 02 Jun 2008, 12:43
 Location: The north side of my town faces east, and the east faces south
Re: Interesting maths problem
souphound wrote:Positive Passion wrote:Surely one has to apply BIDMAS or whatever you call it, so you have
220 x .0.5 = 110.
Then
230  110 = 120.
If the answer really is 5 there's some other trick.
That's the way I see it.
You're both correct in your logic.
There is some other trick. Look closely ...
Last edited by Rorschach on 06 Jan 2022, 14:49, edited 1 time in total.
Bugger off.
 Rorschach
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 Location: The north side of my town faces east, and the east faces south

 Posts: 2013
 Joined: 05 Jul 2017, 23:05
Re: Interesting maths problem
It is beyond a trick, really. If it were a footballer, it would be booked for diving.
 Hightea
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 Joined: 16 Apr 2015, 02:18
 Location: NY state
Re: Interesting maths problem
souphound wrote:Positive Passion wrote:Surely one has to apply BIDMAS or whatever you call it, so you have
220 x .0.5 = 110.
Then
230  110 = 120.
If the answer really is 5 there's some other trick.
That's the way I see it.
yes unless someone is not using BIDMAS
 Rorschach
 Posts: 3745
 Joined: 02 Jun 2008, 12:43
 Location: The north side of my town faces east, and the east faces south
Re: Interesting maths problem
Positive Passion wrote:It is beyond a trick, really. If it were a footballer, it would be booked for diving.
No it isn't!
Have you figured it out then? It's entirely correct mathematically.
Bugger off.
 Rorschach
 Posts: 3745
 Joined: 02 Jun 2008, 12:43
 Location: The north side of my town faces east, and the east faces south
Re: Interesting maths problem
Hightea wrote:souphound wrote:Positive Passion wrote:Surely one has to apply BIDMAS or whatever you call it, so you have
220 x .0.5 = 110.
Then
230  110 = 120.
If the answer really is 5 there's some other trick.
That's the way I see it.
yes unless someone is not using BIDMAS
They are using BIDMAS
Bugger off.

 Posts: 2013
 Joined: 05 Jul 2017, 23:05
Re: Interesting maths problem
Rorschach wrote:Positive Passion wrote:It is beyond a trick, really. If it were a footballer, it would be booked for diving.
No it isn't!
Have you figured it out then? It's entirely correct mathematically.
Probably not. If you regard what looks like a decimal point as a full stop, then the operative phrase becomes 5 = 5, but I guess that is not the answer you are looking for.
 souphound
 World Class Ignoramus
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Re: Interesting maths problem
We are working with base10 numbers, yes?
Footy wrote:Last week, I discovered that the cordless drill I bought about 5 years ago is, in fact, a cordless screwdiver.

 Posts: 2013
 Joined: 05 Jul 2017, 23:05
Re: Interesting maths problem
souphound wrote:We are working with base10 numbers, yes?
You to be working with at least base 6, because otherwise you couldn't have 0.5.
 The Prof
 Trading coffee in Abyssinia
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 Location: A Metropolis of Discontent
Re: Interesting maths problem
It's to do with brackets, isn't it?
(230  220) x 0.5 = should be 5, no?
(230  220) x 0.5 = should be 5, no?

 Posts: 2013
 Joined: 05 Jul 2017, 23:05
Re: Interesting maths problem
The Prof wrote:It's to do with brackets, isn't it?
(230  220) x 0.5 = should be 5, no?
Except that there aren't any brackets.
 OUTPLAY
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 Joined: 24 Apr 2007, 23:21
Re: Interesting maths problem
If there aren't any brackets then the calculation is done in order, right?
Otherwise 230  (220 x 0.5) which comes out as 120
Otherwise 230  (220 x 0.5) which comes out as 120
GoogaMooga wrote:I don't know who it is that is throwing plastic bags overboard from ships, but it certainly isn't me, and I've never met anyone who does that.
 Rorschach
 Posts: 3745
 Joined: 02 Jun 2008, 12:43
 Location: The north side of my town faces east, and the east faces south
Re: Interesting maths problem
Positive Passion wrote:Rorschach wrote:Positive Passion wrote:It is beyond a trick, really. If it were a footballer, it would be booked for diving.
No it isn't!
Have you figured it out then? It's entirely correct mathematically.
Probably not. If you regard what looks like a decimal point as a full stop, then the operative phrase becomes 5 = 5, but I guess that is not the answer you are looking for.
No, it isn't.
Bugger off.
 Rorschach
 Posts: 3745
 Joined: 02 Jun 2008, 12:43
 Location: The north side of my town faces east, and the east faces south
Re: Interesting maths problem
OUTPLAY wrote:If there aren't any brackets then the calculation is done in order, right?
Otherwise 230  (220 x 0.5) which comes out as 120
No. Calculations are done in the order BIDMAS/BODMAS: brackets, of (forget that one), division, multiplication, addition, and, finally, subtraction.
Which is: 230  (220 x 0.5) which comes out as 120
Yet, amazingly, the correct answer is 5!
(Carlsson will get this in a heartbeat)
Bugger off.