Quick Math Question
It takes 9 hours to fill a tank. It takes 11 hours to drain the tank. How long does it take to fill the tank while the drain plug is off, and the tank is draining as you fill?
It takes 9 hours to fill a tank. It takes 11 hours to drain the tank. How long does it take to fill the tank while the drain plug is off, and the tank is draining as you fill?
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1 / (1/9 - 1/11)
common way to pose the same question is a monkey climbing up a pole climbs at 5 ft/hr and then falls 3 ft at the end of each hour - how long to climb a pole of x height.
mistake is to assume net 2ft/hour, but you need to bear in mind that once you reach the top, you don't fall
what job is this for? S&T?
In 1 hour, 1/9 of the tank's volume is filled (V/9) and in 1 hour, 1/11 of the tank's volume is drained (V/11), so effectively, in 1 hour V/9 - V /11 = 2V/99 of the tank is filled. So total time taken is volume/rate = V/(2V/99) = 99/2 hours, or 1/(1/9 - 1/11) as pussinboots said
I loathe this sort of SAT questions... I must have been good at this when I was at HS but now it's simply unbearable. The solution above is very clear but I wouldn't have come up with it on my own.
a coworker asked me and i wanted to confirm my 49.5 before giving it to him. thanks for the help guys - though i had no idea why he had this question, wouldn't tell me :/ -product control
im almost certain this is a problem off of the 11th edition from OG GMAT.
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