Hi - these problems should be very easy for experienced players but an B/I/N player needs to think about the right things in an auction. If you get them wrong, don't feel too bad as long as you understand the rationale for the answers. I'll provide the answers later but I'll put a hint as a spoiler. Try to solve the problem without the spoiler. Also, let me know if you would be interested in seeing more of these from time to time. (Material in blue might be advanced or confusing for some beginners and novices.)
Assume you are playing Standard American (a natural system with 15-17 1NT openings and 5-card majors), IMPS, and nobody is vulnerable.
Let's look at an auction. What is North saying?
If you play a convention called inverted minors with all your partners, this problem set is not for you, but you should be aware that if your 1C opening bid is overcalled, partner's 2C bid is no longer "inverted"; it reverts back to its standard meaning although since partner's 1NT bid now implies a stopper in the overcalled suit, partner will now bid 2C on some hands with only four clubs that would have bid 1NT if the overcall didn't happen.
The SAYC system booklet implies that this auction shows a minimum responding hand (6-10) with five clubs. That is the standard meaning for a raise to 2C. North could have responded 1H or 1S with a four-card or longer major (a higher priority) so North should not have a four-card major. North can also respond 1NT with a weak hand but with five clubs, it is preferable to show support to allow partner to compete if the opponents get active.
While the 2C raise tends to show five, there are times when 1NT is unpalatable and you might choose 2C.
The "textbook" bid may be 1NT but if notrump is going to be played by our side, I would greatly prefer that partner declares as I have no stoppers. Since partner's clubs are weak, it's not likely that bidding 2C will cause partner to overcompete in clubs.
1NT seems wrong with no stoppers in the majors and one of the majors being a small doubleton. You could respond 1D, but what do you do when partner bids 1H? 2C now sounds like you have a lot of cards in the minors. 1NT isn't advisable with no stopper in the only unbid suit. You might not get that lucky - West might overcall a major and East might raise. Do you want to compete to 3C now? You are extremely likely to have more clubs as a partnership than diamonds. I would raise to 2C on this hand also.
These hands are exceptions - the vast majority of the time, the raise to 2C without competition will show five cards.
Now, let's come back to opener. You opened 1C and your partner raised to 2C. What do you do now?
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