♠ 103
♥ AKQ743
♦ 942
♣ 95
♥ AKQ743
♦ 942
♣ 95
♠ J7
♥ 2
♦ KQ10
♣ AQJ8764
♥ 2
♦ KQ10
♣ AQJ8764
♠ Q9642
♥ 1098
♦ A5
♣ K103
♥ 1098
♦ A5
♣ K103
♠ AK85
♥ J65
♦ J8763
♣ 2
♥ J65
♦ J8763
♣ 2
I'm a big fan of The Rule of 2, 3 and 4.
As North in first seat, white vs. red, I counted my tricks. Six. 6 + 4 = 10. Applying this simple math and The Rule, I opened 4♥!
As the cards lie this is the par contract. We have 9 tricks in hearts and they have 10 tricks in clubs. And as so often happens, West was goaded into a 5♣ call, which would have been a below-average spot for them. Preempts work!
Unfortunately partner thought I was advertising 8 hearts, not 6 tricks. He applied The Law of Total Tricks which suggests that we can compete to the level of the number of trumps that we have. 8 + 3 = 11. More simple math. 5♥ says partner.
Down 2, mercifully undoubled, for a 50% score instead of 75%.