Hint
How many large pipes are required to drain the reservoir in 24 hours?
Answer
21 hours and 36 minutes.
Reasoning
Looking at the first clue:
in 12 hours, 6 large pipes can drain 1 reservoir
in 24 hours, 6 large pipes can drain 2 reservoirs
(*) in 24 hours, 3 large pipes can drain 1 reservoir
Looking at the second clue:
in 8 hours, 3 large + 9 small pipes can drain 1 reservoir
in 24 hours, 3 large + 9 small pipes can drain 3 reservoirs
But, by (*), we know that in those 24 hours, 3 large pipes can drain 1 of those reservoirs.
Therefore, the other 2 reservoirs can be drained by the small pipes on their own:
in 24 hours, 9 small pipes can drain 2 reservoirs
in 24 hours, 1 small pipe can drain 2/9 reservoirs
multiply the hours by 9:
in 216 hours, 1 small pipe can drain 2 reservoirs
in 216 hours, 5 small pipes can drain 10 reservoirs
divide the hours by 10:
in 21.6 hours, 5 small pipes can drain 1 reservoir
21.6 hours = 21 hours and 36 minutes.
?
Puzzle 58
Some months have 30 days, some have 31, but how many have 28 days?
My first is in mammoth, but not in elephant.
My second is in racoon, but not in beaver.
My third is in dobbin, but not in horse.
My fourth is in koala, and in kangaroo.
My fifth is in tiger, but not in lion.
My last is in pony, but not in horse.
What am I?
Hint
My first letter is M, and watch out for the 4th letter.
Answer
A monkey.
Reasoning
The 1st letter can be: M O
The 2nd letter can be: C O N
The 3rd letter can be: D B I N
The 4th letter can be: K O A
The 5th letter can be: T G E R
The 6th letter can be: P N Y
??
Puzzle 60
My BrainBashers electronic world atlas has developed another fault.
I listed five countries, and how far away each was from England, and here are the results:
Australia 500 miles
Peru 8,000 miles
India 4,500 miles
Scotland 9,500 miles
France ? miles
