I was recently accepted into Johnson with a 640 GMAT (42Q, 37V). In the interview I was asked not "If" mind you, but "what" I was doing to bolster my quant. She specifically asked me if I was taking any classes to reduce the potential strain of the first semester, which is more intense than most b-schools since all the core is piled into the fall.

Since you're already in Cornell, perhaps you could register for Calc I or Calc II (whichever you haven't taken yet) and intro to statistics over the summer and send a note to your interviewer saying you have done so to be ready for the first semester of Johnson. Hope it helps, and hope to see you there!