Originally Posted by xpi0t0s
I know we have a winner but here's another approach...
Using a few trials work out what angle you have to hold the 4 minute one at for it to time exactly 2 minutes. <obvious after this, so skipped>
Nice approach. But, I fail to understand how you measure "exactly 2 minutes" !! HOW ?! If you have a watch or something to measure "exactly" two minutes, then why go through all this at all ?? Your 7 mins hourglass can't help you too because 2/7 is not something you can "exactly" measure with naked eyes.
Kindly explain your approach "more" clearly. .... To be specific, please explain how you measure "exactly" 2 mins after a few trials ?!