Rounding to Whole Numbers

Date: 04/01/2001 at 23:10:19
From: Leslie
Subject: Rounding whole numbers

Hi, 

Do you know how to round to the nearest whole number? I don't have 
a clue.

Date: 04/02/2001 at 08:38:03
From: Doctor Peterson
Subject: Re: Rounding whole numbers

Hi, Leslie.

We have a discussion of this in our Dr. Math FAQ on the topic, though 
it focuses on decimals:

  http://mathforum.org/dr.math/faq/faq.rounding.html   

The idea is that you want to find the whole number nearest to a given 
number. Suppose that number is 3.4. If we put it on a number line, it 
will look like this:

    0         1         2         3         4         5
    +---------+---------+---------+---------+---------+
                                      ^

It is between two whole numbers, 3 and 4. Which is closer? You can 
tell by looking that 3 is closer to 3.4 than 4 is, so the nearest 
whole number is 3. Is there any quicker way to tell? Well, if the 
number had been 3.5, it would be exactly halfway between 3 and 4; 
since .4 is less than .5, we know that the lower number, 3, is closer.

So the rule is, look at the tenths place (the first digit you will be 
dropping to change the number to a whole number), and see whether it 
is more or less than 5. If it's less than 5, you "round down" to the 
lower whole number; if it's 5 or more, you "round up" to the higher 
number.

If the number you are given is EXACTLY halfway between (like 3.5), 
then there is no nearest whole number, and we just have to choose a 
rule to go by. The usual rule (in schools) is to follow the rule I 
gave above, and round 3.5 up to 4. In more advanced math, other rules 
are sometimes followed in this case, but you don't need to worry about 
that yet.

- Doctor Peterson, The Math Forum
  http://mathforum.org/dr.math/