Last week a maths problem aimed at 15 and 16 year olds in Singapore took the internet by storm.
The logic problem became the new '#thedress' as people worldwide debated what day Cheryl's mystery birthday fell on.
Now a maths question that defeated 96%t of top maths students in America is doing the internet rounds after being republished from 1995 exam papers.
The 'string around the rod' test question was posed to students sitting exams in 16 countries around the world by the International Association for the Evaluation of Educational Achievement.
Here's the answer explained.
The formula applied to this problem is actually a simple Pythagorean theory - nothing too advanced. To get the answer, you have to 'flatten' the rod to give a rectangle of 4 by 12 centimetres.
Jan De Lange explains in Assessing Mathematical Proficiency: "The string unrolls as a straight line, and it first hits the bottom of the rectangle at a distance 1/4 of the length of the cylinder, or 3cm. The next part of the string starts again at the top, hits the bottom 3cm further along, and so on." Then we are left with a breakdown of four right-angled triangles.
Then we apply Pythagorean theorum i.e. a²+ b²=c², which is 3² + 4²=25. The square root of this is 5. When we multiply the pieces of string by four, we get 20 centimetres.
So, were you smarter than a 16-year-old advanced maths student?
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