This is part of our collection of Short Problems.
You may also be interested in our longer problems on Exploring and Noticing.
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problem
Royal arm wrestling
How many arm-wrestles will there be in the royal arm wrestling championship?
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problem
Out of sync
Albert Einstein could see two clocks which were out of sync. For what fraction of the day did they show the same time?
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problem
Take a leaf
An examination paper is made from five pieces of paper. What is the sum of the other page numbers that appear on the same sheet as page 5?
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problem
Halloween day
One year there were exactly four Tuesdays and four Fridays in October. On what day of the week was Halloween.
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problem
How many rectangles?
By drawing 5 horizontal and four vertical lines, one can form 12 rectangles. What is the greatest number of rectangles that can be formed by drawing 15 lines?
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problem
Knockdown
Weekly Problem 51 - 2016
Pegs numbered 1 to 50 are placed in a row. Alternate pegs are knocked down, and this process is repeated. What is the number of the last peg to be knocked down?
Pegs numbered 1 to 50 are placed in a row. Alternate pegs are knocked down, and this process is repeated. What is the number of the last peg to be knocked down?
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problem
Almost constant digits
How many 10-digit numbers containing only 1s, 2s and 3s can you write?
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problem
Too close to call
Weekly Problem 24 - 2012
Can you put these very close fractions into order?
Can you put these very close fractions into order?
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problem
Day of the Triffids
Jasmine buys three different types of plant. How many triffids did she buy?
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problem
Newspaper sheets
From only the page numbers on one sheet of newspaper, can you work out how many sheets there are altogether?
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problem
Collatz-ish
A sequence is generated using these rules. For which values of n is the nth term equal to n?
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problem
Back in time
How many times a day does a 24 hour digital clock look the same when reflected in a horizontal line?
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problem
Oldest and youngest
Edith had 9 children at 15 month intervals. If the oldest is now six times as old as the youngest, how old is her youngest child?
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problem
12345
Repeat a pattern of numbers to form a larger number. Can you find the sum of all the digits?