Question 749110
3 1/2 minutes fills 3/8 of the tank.  Let's see how long it takes to fill 1/8 of the tank.  3/8 / 3 = 1/8, so we'll divide 3 1/2 minutes by 3.  3 minutes 30 seconds/3 = 1 minute 10 seconds.  So each 1/8 of the tank takes 1 minute 10 seconds.  Multiply this number by 8 to get the total time.  
1 minute 10 seconds * 8 = 8 minutes 80 seconds = 9 minutes 20 seconds