We blew it. Had we only known that interpolating and other secrets of grade 11 math - which have proved of absolutely no value to us until now - could turn us into super sleuths like Charlie Eppes, hero of the new CBS series Numb3rs, we would've paid more attention. Unfortunately, when theorems and parallelograms, cosines and tangents were being outlined on the board, we were busy computing batting averages of the 1969 New York Mets. So unlike math whiz Charlie, we can't use complicated mathematical analysis to solve crime. Fortunately for Charlie's brother, Don (an FBI agent), his little brother's always available to help track down a serial killer, or do anything else that'll help fight crime. That's the story behind this new CBS crime show (YES Weekend, Fridays 11:05 p.m., Saturdays 3 p.m.), which borrows substantially from others in the genre, but has the math angle all to itself. After all, says the cool intro, which features mathematical symbols flying across the screen: "Using numbers, we can solve the biggest mysteries we know." Well, maybe not the mystery of just why former Ally McBeal resident noisemaker/flake Peter MacNichol is so badly cast as Charlie's math whiz friend Larry, who wants him to focus on his work and is given to egghead phrases like: "When you're working out human problems, there's always going to be pain and disappointment." Go swallow a protractor, Larry. Rob Morrow stars as Don, and it's a bit strange seeing him go from the wrong side of the law in the gritty Street Time to being a cop here. They've also given our Dr. Fleischman some age wrinkles, or maybe it's just been a long time since Morrow was doing his Alaska thing. Either way, the pairing works pretty well, especially at home, where the brothers listen to aphorisms from their dad, played by former Taxi and Dear John star Judd Hirsch. But what can he know - he's a Dodgers fan. Naturally, when Don's "traditional" investigation methods stall, there's brother Charlie stepping in, and that's when the screen goes all equations on us, spattered with enough symbols to make even Pythagoras cry: "Dayenu!" While it's cool to hear Charlie explain some of his theories - such as why it's impossible to predict exactly where the next drop of water being thrown by a garden sprinkler will fall (but easy to figure out that the water company will charge you big time) - at times the parts of this Hollywood equation don't add up. Sometimes the cliches - like a non-believing boss, assistants who wonder if this stuff really works, etc. - undermine the freshness of the math-to-solve-crimes approach. And some of the writing made us cringe, as when Don turns to Charlie and asks: "You saying you can tell us where the serial killer lives," to which Charlie replies: "Yeah." Whoa, talk about innovative dialogue! There's lots of blackboard scribbling by Don (David Krumholtz, getting his first big role in a series) and a little too much CSI-style lab work, including flashbacks to what the criminal might have done while committing the crime. However, the pace is much faster than what we recall of Mrs. Hellgoth's geometry class. Numb3rs isn't quite in a league with CSI, but it does have a reasonable cast and more plot pluses than minuses. While Hirsch deserves a better part and Morrow's character should chill a bit, watching Don use blackboards to erase crime is more than tangentially entertaining - as long as they don't ask us to do any of those scary age or mixture problems.