Learning to count

I'm getting ready for the scholastic season, and I'm on the lookout for tactics books for beginners.  One of the best I've seen is Dan Heisman's Back to Basics: Tactics (Kindle edition available here).

Heisman argues (quite convincingly, in my opinion) that before one teaches students about pins and forks and such, one first has to teach them not to leave pieces en prise (chess speak for "giving pieces away for free") and to take your opponent's pieces when she leaves them en prise.

Sometimes the answer is rather easy:

White to play

Other things equal, the rook on g3 should eat the pawn on d3: a free pawn is a good thing!

Sometimes the answer is more complicated:

White to play

1.Raxd3 Qxd3 2.Rxd3 Rxd3 is approximately an equal exchange, so the correct answer is "It depends."  (Heisman provides the reader with a more sophisticated point-count system, still suitable for advanced beginners, that suggests that in the general case, the exchange is good for White.)

And sometimes the answer is surprisingly subtle:

White to play

Is the Black pawn safe?  (Three attackers, three defenders)

There are of course other pieces on the board.  To answer Heisman's question, just concentrate on these seven pieces; you may assume that when the missing pieces are taken into consideration, material is equal.

I'll have a few more examples from Heisman in the coming days....