Start with both the hourglasses. When 11 minute's finishes, stop both of them. then turn the 11 minute's hourglass. and start the 13 minute's hourglass. this will give us the 2 minutes in 11 minute's time in that hourglass. and using this we can measure 15 MINUTES.
? + ? + ? + ? + ? = 30
You have to fill numbers in place of question marks. The numbers that you can use are 1, 3, 5, 7, 9, 11, 13 and 15. You can repeat the numbers if you like.
I possess two wires. Both of them have an inconstant thickness but both of them burns completely in sixty minutes. The problem is that I want to measure forty-five minutes while using these two wires.
How can I measure if cutting the wire in half is not possible due to non-homogeneous construction ?
A pair of compasses draws a circle. How, without changing the radius, can you make it draw an oval? You have to fix a radius, then make one rotation from a fixed point to draw an oval where the curvature changes continuously all the way around the perimeter and the pencil produces a doubly symmetrical figure where one axis is more than the unaltered radius. How can it be done?