Source: BBO articles: Seeing through cards By Oren Lidor 
Dealer West. None Vul.
You are playing 4. West lead the AK. When all followed suit, he continued with a 3rd round of clubs which East ruffed with the 2. East returned a spade. You won the trick and tried the Q on which West played the 3.
- How are clubs divided?
- How are hearts divided?
- How are spades divided?
- How are diamonds divided?
- Where is the K?
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How are clubs divided?
West has 4 and East has 2. East ruffed the 3rd club.
How are hearts divided?
West has 4 and East has 5. West opened 1 and then supported 2, which means he has exactly 4 hearts, therefore East has 5.
How are spades divided?
Spades must be 4-4! With 5 cards in spades West would open 1 or East would respond 1 (if he had 5-5 in the majors). Since none of them bid that suit, it breaks 4-4.
How are diamonds divided?
One with West and two with East. You can deduce this by counting the other suits.
Where is the K?
With East. Therefore play the A and watch the K falling (East ruffed a club and by that he stiffed his K).