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
Stop

3 comments:

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.