Can somebody explain this behaviour of Cache (and many other calculating machine as well) : WRITE 1/3*12 4 WRITE 1/3*5

1.666666666666666667

W 1/3*18 5.999999999999999999 W 1/3*21 6.999999999999999999 W 1/3*24 7.999999999999999999 How can we make more occurate caculations in Cache ?