It will be easier if all the decimals were the same length, so add trailing zeroes as necessary: 13.2300, 13.2400, 13.2350, 13.2351. They all begin with 13, so ignore it and the decimal point: 2300, 2400, 2350, 2351. Now it's easy to see the order: 2300, 2350, 2351, 2400. So the order is: 13.23, 13.235, 13.2351, 13.240