OK Guys just a simple question but i can get it through my head.
I want to round off this number to 3 significant digit
Now as far as i know, the rules are
if the two digits following the cutoffpoint is exactly 50 the precedding figure
is not altered if it is an even number.
So following this rule the right answer should be 18.4 right?
The right answer on my book is 18.5. Please help me out!! I cant seem to get why im getting the wron answer! perhaps the book is wrong?
I do not understand your question. When rounding, if the digit to round is 0, 1, 2, 3 or 4, you round towards the bottom, otherwise you round towards the top.
In your case : 18.45056065, rounded to 3 s.f.
Therefore, you want to round off the first "5". Since it is a 5, it will be rounded towards the top, so the "4" becomes a "5". Hence, the correct answer is 18.5
There is no "hard" rule for rounding off number if the digit just after the 'cutoff' is 5.
However, here, since we have many digits given after the 3rd significant digit, you can see that the number 18.45056065 is slightly larger than 18.45 because .00056065 is add to it and so it is slightly closer to 18.5 than it is to 18.4. 18.5 is the correct "round off" as it introduces less error, 0.04943935, than rounding to 184, 0.05056065.