Slater
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| posted on 22/1/19 at 09:01 AM |
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Maths problem
Help....... I used to be good at maths, but my daughter has stumped me with this one:
x = 0.436 (with the 3 and 6 being recurring)
Prove algebraically that x can be written as 24/55
I might post some others.....working through them right now.
Why do they call Port Harcourt "The Garden City"?...... Becauase they can't spell Stramash.
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tegwin
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| posted on 22/1/19 at 09:09 AM |
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24 divided by 55 equals 0.43636363 which equals x therefore x equals 24/55?
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russbost
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| posted on 22/1/19 at 09:48 AM |
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Tegwin, I don't think that counts as an "algebraic proof" 
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Slater
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| posted on 22/1/19 at 09:49 AM |
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Surely it can't be as simple as that, I think there needs to be some algebra in there somehow.
What a strange question.....
Why do they call Port Harcourt "The Garden City"?...... Becauase they can't spell Stramash.
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liam.mccaffrey
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| posted on 22/1/19 at 09:57 AM |
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let x=0.436 recurring
multiply both side by 10 gives
10x= 4.36 recurring
multiply both side by 1000 gives
1000x= 436.36 recurring
therefore (1000x - 10x) = 436.36r -4.36r (this gets rid of the recurring decimal)
This gives
990x = 436-4
990x = 432
rearranging gives
x = 432/990
simplifies to
x= 24/55
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wylliezx9r
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| posted on 22/1/19 at 10:07 AM |
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24/55=0.436=x
24=0.436*55=55X
24= 23.98 = 55x
23.98/24 = 55X/24
23.98/4 CANCELS DOWN TO 1 (OR WOULD OF IF I HAD A PROPER CALCULATOR WITH RECURRING FUNCTION)
LEAVING 55X/24
REARANGED X =24/55
[Edited on 22/1/19 by wylliezx9r]
I spent a lot of money on booze, birds and fast cars. The rest I just squandered.
George Best
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Slater
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| posted on 22/1/19 at 10:48 AM |
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Nice, you boys are cleverer than you look. I think Liams' solution is right, I would not have come up with that.
What a great forum this is. Thanks both.
Why do they call Port Harcourt "The Garden City"?...... Becauase they can't spell Stramash.
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rusty nuts
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| posted on 22/1/19 at 11:37 AM |
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If you had asked this question 50 years ago I would have worked it out in my head.
What was the question?
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nick205
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| posted on 22/1/19 at 11:55 AM |
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I have similar difficulties helping my kids with their maths homework.
I didn't find maths difficult at school, but age has bitten and my brain power isn't what it used to be.
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Mr Whippy
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| posted on 22/1/19 at 12:20 PM |
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the answer is 42
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liam.mccaffrey
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| posted on 22/1/19 at 01:31 PM |
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How old is your daughter, that problem is far too difficult for GCSE. A-level maybe.
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Angel Acevedo
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| posted on 22/1/19 at 03:21 PM |
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quote:
Originally posted by rusty nuts
If you had asked this question 50 years ago I would have worked it out in my head.
What was the question?
No wonder there´s "rusty" on your forum name...
50 years ago I´d have mumbled "gu-gu-da-da"
Beware of what you wish.. for it may come true....
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wylliezx9r
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| posted on 22/1/19 at 03:43 PM |
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quote:
Originally posted by Slater
Nice, you boys are cleverer than you look. I think Liams' solution is right, I would not have come up with that.
What a great forum this is. Thanks both.
I think you'll find both solutions are correct but just done in different ways. I haven't been able to show all the working with my method
- it's very difficult to show the cross cancellation and re-arrangement but its very basic algebra probably A-level.
I spent a lot of money on booze, birds and fast cars. The rest I just squandered.
George Best
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SteveWalker
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| posted on 22/1/19 at 04:00 PM |
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quote:
Originally posted by nick205
I have similar difficulties helping my kids with their maths homework.
I didn't find maths difficult at school, but age has bitten and my brain power isn't what it used to be.
I can still do the maths they do today - once I can figure out the meaning of the question. So many terms and methods seem to have changed names.
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02GF74
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| posted on 22/1/19 at 04:55 PM |
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quote:
Originally posted by wylliezx9r
quote:
Originally posted by Slater
Nice, you boys are cleverer than you look. I think Liams' solution is right, I would not have come up with that.
What a great forum this is. Thanks both.
I think you'll find both solutions are correct but just done in different ways. I haven't been able to show all the working with my method
- it's very difficult to show the cross cancellation and re-arrangement but its very basic algebra probably A-level.
Sorry but no. , Liam subtraction gets rid of the recurring sequence, whereas yours would only work if you had a calculator that can represent decimals
to an infinite number of places, which don't exist.
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steve m
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| posted on 22/1/19 at 07:00 PM |
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Im with Mr Whippy,
42
Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at
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Andybarbet
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| posted on 22/1/19 at 08:04 PM |
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42 Spot on :-)
Give a man a fish & it will feed him for a day, give him a fishing rod & you've saved a fish.
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Slater
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| posted on 22/1/19 at 08:40 PM |
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Hi, daughter is 15, doing GCSE Maths level 1. I took Maths O level age 15 and somehow got an A, but that question stumped me.
She says a big thank you to Liam, and that Mr Whippy must be a fool.
Obviously too young for HHGTTG.
Why do they call Port Harcourt "The Garden City"?...... Becauase they can't spell Stramash.
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liam.mccaffrey
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| posted on 22/1/19 at 09:54 PM |
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I knew that maths degree would come in handy........one day
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nick205
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| posted on 23/1/19 at 09:27 AM |
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quote:
Originally posted by Angel Acevedo
quote:
Originally posted by rusty nuts
If you had asked this question 50 years ago I would have worked it out in my head.
What was the question?
No wonder there´s "rusty" on your forum name...
50 years ago I´d have mumbled "gu-gu-da-da"
50 years ago I don't think I was even a thought in my parents heads (I'm the oldest of 3 children by the way)
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Mr Whippy
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| posted on 23/1/19 at 12:29 PM |
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quote:
Originally posted by Slater
Help....... I used to be good at maths, but my daughter has stumped me with this one:
x = 0.436 (with the 3 and 6 being recurring)
Prove algebraically that x can be written as 24/55
I might post some others.....working through them right now.
anyway why are you doing her home work? tell her to do it herself the cheater
I've probably forgot 99% of the maths I got at school, makes not difference tbh, I have excel here to do it for me or google if I get stuck
I'm just waiting for the micro chip they stick in your head that gives you access to the internet just by the power of thought 
Then I'll be
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JoelP
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| posted on 29/10/24 at 11:47 AM |
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Was just helping my lad revise for his gcse, and recurring numbers came up, and I actually remembered this thread from 6 years ago! Crazy. Didn't
help me solve it to be honest though. I did my maths gcse when I was 11, and I swear these things didn't come up.
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Rod Ends
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| posted on 29/10/24 at 12:55 PM |
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With the prompt:
x = 0.436 (with the 3 and 6 being recurring)
Prove algebraically that x can be written as 24/55
ChatGPT gives:
To prove that x = 0.4363636... (where the digits 3 and 6 repeat can be written as 24/55 algebraically, let’s set up the problem and solve it
step-by-step.
1. Let x = 0.4363636...
2. Since the repeating part is "36," we’ll separate this into two parts: the non-repeating "4" and the repeating
"36."
3. Let x = 0.4 + 0.0363636...
4. Now let y = 0.0363636... , which is the repeating decimal part.
Then, we can write x = 0.4 + y
5. To express y as a fraction, set y = 0.0363636...
6. Multiply y by 100 (since "36" has two digits:
100y = 3.6363636...
7. Now, subtract y = 0.0363636... from 100y = 3.6363636... to eliminate the repeating decimal:
100y - y = 3.6363636... - 0.0363636...
99y = 3.6
8. Solve for y :
y = 3.6/99 = 36/990 = 4/110 = 2/55
9. Substitute y = 2/55 back into x = 0.4 + y :
x = 0.4 + 2/55
10. Rewrite 0.4 as a fraction:
0.4 = 4/10 = 22/55
11. Therefore:
x = 22/55 + 2/55 = 24/55
So, we have shown algebraically that: x = 24/55
[Edited on 29/10/24 by Rod Ends]
[Edited on 29/10/24 by Rod Ends]
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David Jenkins
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| posted on 30/10/24 at 01:58 PM |
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I see questions like this and think... "I wonder what's on the TV".
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Rod Ends
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| posted on 30/10/24 at 03:38 PM |
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[img]
 
OU maths
[/img]
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