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General => General Discussion => Topic started by: mightytiges on November 03, 2015, 04:44:11 AM

Title: Two 50 cents - the maths puzzle
Post by: mightytiges on November 03, 2015, 04:44:11 AM
This question was apparently on the VCE maths exam and freaked out the kids lol.

(http://www.smh.com.au/cqstatic/12z7v7/fiftyQuestion729px.jpg)
Source: The Age
Title: Re: Two 50 cents - the maths puzzle
Post by: taztiger4 on November 03, 2015, 07:42:49 AM
D
Title: Re: Two 50 cents - the maths puzzle
Post by: 1965 on November 03, 2015, 07:56:31 AM
D

Genius
Title: Re: Two 50 cents - the maths puzzle
Post by: taztiger4 on November 03, 2015, 08:04:49 AM
D

Genius

Thanks, did you get it wrong ?
Title: Re: Two 50 cents - the maths puzzle
Post by: 1965 on November 03, 2015, 08:15:56 AM
D

Genius

Thanks, did you get it wrong ?

Nah, visually it looks like an equilateral triangle.
Title: Re: Two 50 cents - the maths puzzle
Post by: mightytiges on November 03, 2015, 03:55:54 PM
D

Genius

Thanks, did you get it wrong ?

Nah, visually it looks like an equilateral triangle.
You can solve it without assuming it's an equilateral triangle  ;).

* One full rotation of any polygon is 360 degrees.
* One full rotation of a dodecagon (50 cent coin) involves 12 turns.
* So each turn of the 50 cent coin is 360/12 = 30 degrees.
* Joining two 50c coins together thus gives you X = 2 x 30 = 60 degrees
Title: Re: Two 50 cents - the maths puzzle
Post by: Smokey on November 03, 2015, 05:46:09 PM
Lol, exactly how I solved it MT.
Title: Re: Two 50 cents - the maths puzzle
Post by: Yeahright on November 03, 2015, 05:54:56 PM
D

Genius

Thanks, did you get it wrong ?

Nah, visually it looks like an equilateral triangle.

 :lol Glad you weren't my teacher.

Here's you revision kids, if the triangle looks like it's got a 60 degree angle then circle it cause it'd be right
Title: Re: Two 50 cents - the maths puzzle
Post by: dwaino on November 03, 2015, 07:11:44 PM
F) all of the above

would have been my answer.
Title: Re: Two 50 cents - the maths puzzle
Post by: 1965 on November 03, 2015, 09:47:22 PM
D

Genius

Thanks, did you get it wrong ?

Nah, visually it looks like an equilateral triangle.

 :lol Glad you weren't my teacher.

Here's you revision kids, if the triangle looks like it's got a 60 degree angle then circle it cause it'd be right

You do not know what you are talking about.

Multiple choice questions aren't about solving a problem they are about guessing the correct answer.

 :cheers

Title: Re: Two 50 cents - the maths puzzle
Post by: 1965 on November 04, 2015, 05:31:47 AM


OK, how to guess the answer in about 10 seconds

1. draw a line out from the corner of the angle at a 90 deg angle to the edge of the coin

2. draw another line out at 45 deg (ie half 90 deg)

3. look at your drawing and you can immediately discard options a, b and c.

4. the angle looks more like 60 than 75.

5. move on to the next question (time is important in exams)

 :thumbsup
Title: Re: Two 50 cents - the maths puzzle
Post by: Smokey on November 04, 2015, 12:00:59 PM
By the time it took me to draw the 2 lines I would have worked out 360/12*2 in my head, written it down and moved on.  Stop trying to complicate things!   ;D
Title: Re: Two 50 cents - the maths puzzle
Post by: dwaino on November 04, 2015, 12:55:08 PM
Ignoring my previous answer (since you don't pass electrical trade school at over 90% if you're a chump at trig), I thought the most obvious answer is 60 because the sides are all clearly even and 60*3=180. Done, no drawing, no extra calculations, nothing.
Title: Re: Two 50 cents - the maths puzzle
Post by: 1965 on November 04, 2015, 12:56:57 PM
By the time it took me to draw the 2 lines I would have worked out 360/12*2 in my head, written it down and moved on.  Stop trying to complicate things!   ;D

Which is fine for you but we are talking about Further Maths students.

Remember all the good Maths students do Methods and Specialist.

 :cheers
Title: Re: Two 50 cents - the maths puzzle
Post by: 1965 on November 04, 2015, 12:58:27 PM
Ignoring my previous answer (since you don't pass electrical trade school at over 90% if you're a chump at trig), I thought the most obvious answer is 60 because the sides are all clearly even and 60*3=180. Done, no drawing, no extra calculations, nothing.

Indeed but you need to know that the three angles of a triangle add to 180 and that all three angles are equal.

Fine for some students but not for all.

 :cheers
Title: Re: Two 50 cents - the maths puzzle
Post by: Smokey on November 04, 2015, 02:53:09 PM
By the time it took me to draw the 2 lines I would have worked out 360/12*2 in my head, written it down and moved on.  Stop trying to complicate things!   ;D

Which is fine for you but we are talking about Further Maths students.

Remember all the good Maths students do Methods and Specialist.

 :cheers

Which is all well and good if you are a current day student/teacher that has any clue about the mathematical academic definitions of "Further Maths", "Methods" or "Specialist".  For someone who matriculated in 1975 it was General Maths for the everyday student or Pure and Applied Maths for the propeller heads like Dwaino.   ;D

So I will stick with my simple, quick method of solving the equation in my head and moving on to the next exam question before I even have time to think about drawing pretty lines.   :snidegrin
Title: Re: Two 50 cents - the maths puzzle
Post by: 1965 on November 04, 2015, 03:31:40 PM
By the time it took me to draw the 2 lines I would have worked out 360/12*2 in my head, written it down and moved on.  Stop trying to complicate things!   ;D

Which is fine for you but we are talking about Further Maths students.

Remember all the good Maths students do Methods and Specialist.

 :cheers

Which is all well and good if you are a current day student/teacher that has any clue about the mathematical academic definitions of "Further Maths", "Methods" or "Specialist".  For someone who matriculated in 1975 it was General Maths for the everyday student or Pure and Applied Maths for the propeller heads like Dwaino.   ;D

So I will stick with my simple, quick method of solving the equation in my head and moving on to the next exam question before I even have time to think about drawing pretty lines.   :snidegrin

 :sleep
Title: Re: Two 50 cents - the maths puzzle
Post by: Yeahright on November 04, 2015, 05:04:55 PM
Don't forget the smarter kids do VCE as it is. The dummies (and some smart people who already have a career as a tradie planned) do VCAL maths (Foundations)
Title: Re: Two 50 cents - the maths puzzle
Post by: Yeahright on November 04, 2015, 06:16:29 PM
Shame too. A lot of bright people go down that path simply because that's where they want to be not because they think it's their only choice