You might not have access to a calculator, so when times comes like this when you have to validate a statement if wrong or right, mental math comes in help.
You only need the approximate number to do something like mental math. Both numbers divided by each other, is really close to their whole numbers of 1 and 5, respectively. If you divide 1/5, you get 0.2, which is not what the answer is. 0.02 and 0.2 are very different answers, and you would not get 0.02 no matter how many decimals after that 1.0 and 5.0.
Which means the statement is not true based on logic and mental math.
