Monday, September 24, 2012

You are given two hourglasses. One measures 4 minutes and one measures 7 minutes. How would you measure exactly 9 minutes?

StepTime4 minute timer7 minute timer
10 minStartStart
24 minsFlip3 minutes left
37 mins1 minute leftFlip
48 minsStopFlip (1 minute left)
59 mins


AliasNeo015 said...

This is outright wrong!!

Shashank Narayan said...

@AliasNeo15 ..tell us correct solution ?

Anonymous said...

No idea what's going on in your step 4. I don't think it's possible without some working up to the start of the timing:

Start 4 and 7.
Start 4 again when it runs out.
7 runs out, 1m left on 4. Start timing the 9 minutes now.
Just let 4 run out, then run it twice more.