The school maths question dividing the internet

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1286 posts

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#1420839 4-Nov-2015 14:43

I still remember from high school geometry (and it has been 38 years since I did high school geometry) that the exterior angles of a polygon add up to 360°. The 50c piece has 12 angles, so 360÷12=30. There are two 50c pieces side-by-side, so the angle at the point the two coins meet is 2×30=60°. For kids who should have learned this stuff within a year or two of sitting the exam, I'm surprised at all the fuss it has created.

keewee01

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#1420843 4-Nov-2015 14:45

It was easy - got the answer in seconds by basic visual deduction, then did a quick bit of maths which confirmed my answer.

Any OK year 12 student shouldn't have an issue with getting the answer, I know that my year 9 son will be able to quickly work it out.

n4

959 posts

Ultimate Geek

#1420844 4-Nov-2015 14:45

sbiddle: I'd love to know where all the people are on the internet that are supposedly stumped by this. I haven't come across any.

Well they are not going to be on geekzone, clearly :-) However out in the real world the number of people that remember the exterior angles of a polygon add up to 360 degrees would be tiny...I didn't and I'm an engineer (albeit non-mechanical).

Having said that - it was pretty easy to work out knowing the edge of the coin takes three 'turns' to go from horizontal to vertical, therefore 30 degrees at a time, therefore 60 degrees.

Entirely appropriate for a school question, but probably too easy for Year 12. What surprises me is the expectation that any sizable portion of the population at large would still be able to pass Year 12 maths...

Samsung Note20 Ultra, on 2degrees

MikeB4

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#1420850 4-Nov-2015 14:51

The answer to this question HOW DO YOU SOLVE THE 50 CENT COIN MATH QUESTION? is easy. Don't use cheap coins from across the ditch use this.....

Will never need to find the answer

JoshWright

398 posts

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#1420871 4-Nov-2015 15:09

I'm a current Year 12 Level 2 NCEA student.. Took me all of 10s to work it out? Really not that difficult. I've known the external angles of a polygon rule since maybe Year 10?

BinaryLimited

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#1420872 4-Nov-2015 15:15

Binary Limited - Safe. Secure. Simple. ™
www.binarylimited.co.nz

surfisup1000

5288 posts

Uber Geek

#1420875 4-Nov-2015 15:20

Jaxson: This took me about 10 seconds. How is this difficult?

That may sound knoby but I found that china (?) car parking sequence one WAY more difficult, and that was for 7 year olds...

87, not really a math question though. More a psychological trick.

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surfisup1000

5288 posts

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#1420881 4-Nov-2015 15:26

How about this one ... it is a psychological trick rather than a math prob as such.

If a baseball and a bat cost $1.10 together, and the bat costs $1.00 more than the ball, how much does the ball cost?

Inphinity

2780 posts

Uber Geek

#1420886 4-Nov-2015 15:30

surfisup1000: How about this one ... it is a psychological trick rather than a math prob as such.

If a baseball and a bat cost $1.10 together, and the bat costs $1.00 more than the ball, how much does the ball cost?

$0.05

surfisup1000

5288 posts

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#1420889 4-Nov-2015 15:31

Inphinity:
surfisup1000: How about this one ... it is a psychological trick rather than a math prob as such.

If a baseball and a bat cost $1.10 together, and the bat costs $1.00 more than the ball, how much does the ball cost?

$0.05

Yes , but what did you want to say :)

yitz

2074 posts

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#1420890 4-Nov-2015 15:31

kiwitrc

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#1420894 4-Nov-2015 15:39

yitz:

$0.05

wasabi2k

2096 posts

Uber Geek

#1420898 4-Nov-2015 15:42

surfisup1000: How about this one ... it is a psychological trick rather than a math prob as such.

If a baseball and a bat cost $1.10 together, and the bat costs $1.00 more than the ball, how much does the ball cost?

I knew this was a trick one - doubted myself, but it makes more sense when you state it as (x+1) + x = 1.10

as for the coin one - the 360 degree thing came back to me... it's only been 15 years since I actually did any geometry.

Inphinity

2780 posts

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#1420903 4-Nov-2015 15:45

surfisup1000:
Inphinity:
surfisup1000: How about this one ... it is a psychological trick rather than a math prob as such.

If a baseball and a bat cost $1.10 together, and the bat costs $1.00 more than the ball, how much does the ball cost?

$0.05

Yes , but what did you want to say :)

That was what I wanted to say. I imagine quite a few people say $0.10 though.

Inphinity

2780 posts

Uber Geek

#1420904 4-Nov-2015 15:45

yitz:

The bus is presumably going straight ahead.

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