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Rule of Three
If it takes four men one day to build a wall, how long does it take 60,000 men to build a similar wall?
Crossing the Atlantic
Every day at noon a boat leaves Le Havre for New York while another boat leaves New York for Le Havre. The ocean crossing takes seven days. How many boats will each boat cross during their journey?
On Time
On a clock the three hands - the second, minute and hour hands - are on the same axis. How often in a 24 hour day will the second hand be parallel to either of the two other hands?
Age 11 to 14
Challenge Level
Where are the travelling buses positioned when a new pair of buses is due to leave?
How soon after leaving will a bus meet a bus travelling from the opposite direction?
Will it be the same for the first bus of the day as for the buses travelling in the middle of the day?
How soon after leaving will a bus meet a bus travelling from the opposite direction?
Will it be the same for the first bus of the day as for the buses travelling in the middle of the day?
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NRICH is part of the family of activities in the Millennium Mathematics Project.
NRICH is part of the family of activities in the Millennium Mathematics Project.