Independent Pursuits: Puzzle
Thursday 18 June 1998
Four men have to cross a river. There is only one boat, and it will hold only two at a time. The boat will not go across the river on its own. Because the men are of vastly different bulk, the time they take to cross the river varies. From slowest to fastest they take 10, 5, 2 and 1 minute respectively. When two are together, the boat crosses at the rate of the slower. What is the shortest time it takes to get all four across the river? (Answer tomorrow).
Yesterday's answer: (brackets indicate weights in same scale)
1. (R1+B1) : (R2+W1)
If they balance, try: (B2) : (W2). One will be heavier, if B2, then B2, R1 and W1 are the heavy balls.
If the first weighing does not balance, try: (B1) : (W2). The result will enable everything to be deduced.
Arts & Ents blogs
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- 2 Oil tanker with $100 million cargo goes missing off Texas coast
- 3 George Galloway left with severe bruising after attack in Notting Hill by man 'shouting about the Holocaust'
- 4 Lady al-Qa’ida: On the trail of Dr Aafia Siddiqui, the world’s most wanted prisoner
- 5 A teacher speaks out: 'I'm effectively being forced out of a career that I wanted to love'
Robin Williams Emmys tribute led by Billy Crystal criticised for including 'racist' joke about Muslim woman
The Rotherham child abuse scandal is a tale of apologists, misogyny and double standards
What do immigrants really think of Britain? Polish immigrant's Reddit post goes viral
Scottish independence TV debate: Pumped-up Alex Salmond bounces back in bruising second round against Alistair Darling
Do you realise just how foolish the UK looks?
With Douglas Carswell joining Ukip, my party has taken another giant step forward
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