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Completely Off-Topic / Trick questions!
« on: May 03, 2004, 10:30:36 am »Quote from: "Laura"
Using 1 drain, a swimming pool can be emptied in 45 minutes. Using a different drain, the job requires 1 hour and 15 minutes. How long will it take if both drains are opened?
D1 empties pod in 45mins
D2 empties pod in 75mins
in 1 min-
D1 empties 1/45 of pod
D2 empties 1/75 of pod
together in 1 min 1/45 + 1/75 =
75/3375 + 45/3375 =
15/675 + 9/675 =
24/675 of the pod empties in 1 min
1/675 empties in 1min / 24 = 0.416666(r) so...
pool empties in 675x0.416666(r) = 28.125
675/24 = 28.125mins
= 28mins 71/2 secs
Quote from: "Laura"
next question: One pipe can fill a tank in 4 hours. A second pipe also requires 4 hours, but a third needs three hours. How long will it take to fill the tank if all three pipes are open?
in 1 hour-
pipe A fills 1/4 tank
pipe B fills 1/4 tank
pipe C fills 1/3 tank
1/4 + 1/4 + 1/3 =
3/12 + 3/12 + 4/12 =
10/12 in 1 hour therefore,
1/12 tank filled in 6x12 mins
= 72mins or 1hour 12mins
edit: oops in my eagerness i didnt c this was answered.