♠ K J 2
J 10 7
A Q 10 4
♣ 9 6 4
South is playing 3NT. Your partner, West, leads the 6.
You play the A and South follows with the 9.

How will you defend? (scroll down)
♠  

 
♣  
N
W        E
S
♠ 10 8 5 4
A 8 4
K 8
♣ Q J 7 3
♠  
 
 
♣  
















♠ K J 2
J 10 7
A Q 10 4
♣ 9 6 4
South is playing 3NT. Your partner, West, leads the 6.
You play the A and South follows with the 9.

Using the Rule of Eleven tells you North, East and South began with 5 s bigger than the 6.
Dummy had 3 and you had 2, so that accounts for all 5. BUT SOUTH PLAYED THE 9!

Does this mean the Rule of Eleven is wrong???
Not at all, the Rule is just fine.
But it only applies when the opening lead is a 4th-down lead. So you conclude that partner must have led top of nothing from a weak suit. So rather than return a you play a small ♣, trying for some tricks in that suit.

You can see that this approach will pay off, but just playing back a useless would hand South the contract.
♠ 9 7 3
6 5 4 2
7 6 5
♣ K 5 2
N
W        E
S
♠ 10 8 5 4
A 8 3
K 8
♣ Q J 7 3
♠ A Q 6
K Q 9
J 9 3 2
♣ A 10 8