Using the BrainTracker grid below, how many words can you find? Each word must contain the central F and no letter can be used twice, however, the letters do not have to be connected. Proper nouns are not allowed, however, plurals are. Can you find the nine letter word?

Hint: The exact size of the pipes and reservoir does not matter.

Answer: 21 hours and 36 minutes.

The exact size of the pipes and reservoir does not matter. If we label the large pipes L, the small pipes S and if the reservoir has a total of T litres, then:

T ÷ 6L = 12 which means L = T ÷ 72

and

T ÷ (3L + 9S) = 8 which means that S = T ÷ 108

we want

T ÷ 5S which gives 108 ÷ 5 hours = 21.6 hours = 21 hours and 36 minutes.

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