Silly problem with a switch and numbers

1

I don’t understand why my switch statement isn’t working. Could somebody help me here im perplexed.


   var thisSquareFt:Number = (thisWidth*thisLength)/144   
   trace("square footage :" + thisSquareFt);
   
   //Find the pricing based on square footage
   switch(thisSquareFt) {
    case (thisSquareFt > 0 && thisSquareFt <=5):
     thisSquarePrice = 7;
     break;
    case (thisSquareFt > 5 && thisSquareFt <=10):
     thisSquarePrice = 6;
     break;
    case (thisSquareFt > 10 && thisSquareFt <=15):
     thisSquarePrice = 5;
     break;
    case (thisSquareFt > 15 && thisSquareFt <=30):
     thisSquarePrice = 4;   
     break;
    case (thisSquareFt > 30):
     thisSquarePrice = 3;   
     break;
    default :
     thisSquarePrice = 999
   }

So I can see from my trace that thisSquareFt is definitely a number yet none of my cases trigger. The value was NaN before I set a default. Why aren’t my conditional statements working?

Thanks