The founders of tennis meant to create triangular courts, but geometry was especially challenging before the invention of numbers that weren’t 15, 30, 40, and deuce. Make every point count with today's Groupon: for $99, you get four one-hour group tennis lessons (a $180 value) at one of four locations in and around the city: Manhattan Plaza Racquet Club, Roosevelt Island Racquet Club, New York Tennis Club, and Eastside Tennis Club during all club hours. Groupon holders also get a one-month membership at either Manhattan Plaza Racquet Club or Roosevelt Island Racquet Club (up to a $145 value), and use of a demo racquet and balls (a $25 value), bringing this deal's total value to $350.

The Wimbledon-weathered teachers of Roosevelt Island Racquet Club and the other swinging locations arm their pupils with world-class expertise from top-ranked international players. Atop New York Tennis Club's and Roosevelt Island's clay courts or the hardtops of the others, students congregate once weekly to work on their forehands, backhands, overheads, and underfoots in a lively series of games and drills (buyers may rank their preferred schedule online). This deal also includes 15% off racquet purchase or restringing, tennis balls, demo racquets and balls for loan, and a one-month membership to the clubs, granting temporary access to the clubs' game-arranging services and exclusive rates on programs, workshops, and open-court reservations (summer rates for members range from $50–$68/hour, about $35 less than non-member fees), as well as exclusive tips for bleaching accidentally tie-dyed tennis whites.