It goes back to 1917, when Japanese mathematician Sichi Kakeya posed the following puzzle: given an infinitely thin needle of unit length, what is the smallest amount of space you can sweep out ...

All you need is a spare toothbrush. To execute the trick, lay some of your thread across the bristles of the brush. Then simply press the eye of the needle downwards over the thread. The bristles ...

For those who couldn’t spot the needle, don’t worry. Check the answer below. If you enjoyed solving this tricky picture puzzle challenge, SHARE this viral picture puzzle with your friends and ...