I thought this was the most difficult puzzle yet. I actually had to get the pen and paper out to try and work it out.
I got to 9 mops for 27 days easily enough. But then struggled on the last 3 days. My first guess was 12.
But after this was wrong, it took me a good 10 minutes to work out how to use the final mop.
Think about how many mops should be necessary for 30 days. Then see if there is any way you can reduce that number.
Each mop has to dry for two days, so you will need three mops for the first three days. It will take nine days until these mops are broken. Try to apply this pattern to the whole month.
If three mops are used over nine days, then nine mops are used to clean for 27 days.
How many mops are needed for the remaining three days? Try to think about the smallest number needed.
The key is in thinking about how you will divide up the remaining three days. If you leave it until the end of the month, you will need three mops, but what would happen ifyou spread these days out throughout the month?
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