Nope, only MBA 11" is 16:9. Everything else apple-laptop is 16:10. Been for a while now. (You can also calculate that from the resolution 2560*1600)
Pythagoras rule for right-angled triangle.
You have two known legs (16 and 10) which means the hypothenuse is (c^2=a^2+b^2) (look up right-angled triangle calculation)
Now these are ratios, the hypothenuse is 13.3"
math goes as follows:
c = square root of (16*16 + 10*10)
c =~18.9
Now we know c is 13.3 and that it is 18.9 in size compared to A and B...
so (13.3/18.9) * 16 for width
and (13.3/18.9) * 10 for height