Question from past CSSE Maths Paper

devg · Post by **devg** » Sat Oct 11, 2008 5:55 pm

I am confused with this question.

The diagram shows a circle with circumference of 1 cm being rolled around an equilateral triangle with sides of 1 cm length. How many complete turns does the circle make as it rolls around the triangle (without slipping) to it's original starting position.

The correct answer is 4, however I thought that the answer was 3. Can anyone please explain the logic here?

Thanks in advance

essex-mum18 · Post by **essex-mum18** » Sat Oct 11, 2008 6:51 pm

Hi

This is from last year (2008) Math paper. I hope the following info helps

http://www.elevenplusexams.co.uk/forum/ ... php?t=5383

moved · Post by **moved** » Sun Oct 12, 2008 11:47 am

This is a problem from the junior maths challenge, aimed at bright year 8 pupils.

The penny has to turn the corners, it doesn't jump. If you roll a real penny around a triangle, with a dot on the penny at the corner, you can see how it turns 1/3 of a turn.

Horrid question, I tell my pupils to have a go at the last question on the paper and not to worry too much if they can't do it.

Drawing always helps.

devg · Post by **devg** » Thu Oct 16, 2008 9:59 pm

It is indeed quite difficult question. I took some time to understand, but now can explain it to my daughter. Thanks a lot

Nippy43 · Post by **Nippy43** » Wed Dec 24, 2008 8:50 am

I took the exam with this question. We bought the past paper for my brother to practice as he is doing it next year. I put 3 and got it wrong. The answer booklet says it is 4 but I have no idea why. I still got in though!