Rounding Off Examples
Example 1
Round 23.437 8 to three sig figs.
Look at the number to the immediate right of the 4. In this case, the number is
less than 5, so drop it, plus all the decimals further to the right, and leave the
4 as is.
The answer is 23.4
Example 2
Round 23.477 8 to three sig figs.
In this case the number to the right of the 4 is greater than 5, so drop it and
all the other decimals to the right, and increase the 4 by one.
The answer is 23.5
Example 3
Round 23.457 8 to three sig figs.
Here is a case where the number to the right of the 4 is a 5. Since the
remaining decimals (7 and 8) are also known, it is easy to see that the entire
number is more than half way between 23.4 and 23.5. Round up.
The answer is 23.5
Example 4
Round 23.45 to three sig figs.
In this case, the number to the right of the 4 is exactly 5. No more decimals
are given. The rule here tries to balance rounding up with rounding down.
These types of numbers are always rounded so that the result ends up to be an
even number. Since half of all numbers are even, and half are odd, then
rounding in this way should balance things out.
The answer is 23.4
Note: if the initial number is 23.55, then it is rounded up to 23.6 to make the
final result even.