Two 50 cents - the maths puzzle

[mightytiges]

This question was apparently on the VCE maths exam and freaked out the kids lol.


Source: The Age

[taztiger4]

D

[1965]

D

Genius

[taztiger4]

D

Genius

Thanks, did you get it wrong ?

[1965]

D

Genius

Thanks, did you get it wrong ?

Nah, visually it looks like an equilateral triangle.

[mightytiges]

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. 

[Smokey]

Lol, exactly how I solved it MT.

[Yeahright]

D

Genius

Thanks, did you get it wrong ?

Nah, visually it looks like an equilateral triangle.

  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

[dwaino]

F) all of the above

would have been my answer.

[1965]

D

Genius

Thanks, did you get it wrong ?

Nah, visually it looks like an equilateral triangle.

  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.

 

[1965]

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)

 

[Smokey]

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!   

[dwaino]

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.

[1965]

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!   

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

Remember all the good Maths students do Methods and Specialist.

 

[1965]

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.