GMATD11 wrote:
An empty pool being filled with water at a constant rate takes 8hours to fill to 3/5 of its capacity.how much more time will it take to finish filling the pool?
A. 5hr 30min
B. 5hr 20min
C. 4hr 48min
D. 3 hr 12min
E. 2hr 40 min
45-second approach: Find rate of filling. Find work remaining. Find time needed to finish: Work divided by rate equals time (to fill volume that needs filling).
What is rate of filling?
\(\frac{Work}{time} = rate\)RATE = \(\frac{(\frac{3}{5})}{8} = (\frac{3}{5}*\frac{1}{8})= \frac{3}{40}\)
How much work remaining?
\(1 - (\frac{3}{5}) = (\frac{5}{5} - \frac{3}{5})= \frac{2}{5}\)
How much time to finish remaining work?
\(\frac{Work}{rate} = time\)Work remaining = \(\frac{2}{5}\)
Rate = \(\frac{3}{40}\)
\(\frac{(\frac{2}{5})}{(\frac{3}{40})}\) =
\(\frac{2}{5} *
\frac{40}{3} = 5\frac{1}{3}hrs\)
Multiply
any fraction of an hour by 60 to get minutes.* In cases where you already have the hours, and you need hours plus minutes, use
only the fraction. (Do not include the 5 here.)
\(\frac{1}{3}hr * 60 =\) 20 minutes
\(5\frac{1}{3}hrs\) = 5 hours, 20 minutes
Answer B
*
Because:
\(\frac{1hr}{3} * \frac{60min}{1hr} =\) 20 minutes, where hours cancel
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