It's entirely too early, and I am clearly not awake yet. As soon as I made my last post the answer came to me. At least I think it did. Tell me is my math on point?
width
2x - 1/2x = 42
1.5x = 40
x=28
length
2x -1/2x = 60
1.5x = 60
x=40
28x40=1120
So I'd need 1120 2 inch squares (1.5 inch finished) for a lap quilt that was 42x60?