Answers

2014-09-16T16:35:11+08:00
The tank is full when half of an hour ( 30 mins. ) 

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2014-09-16T17:27:32+08:00
15 minutes, why? because it stated that in a minute it doubles, in an hour it will be full, 30x2=60 this is already full, 15x2=30 this is half, 1hr=60min.
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