It helps to start every post by saying where you are in school, fourth grade or college senior. That way we can give you an answer that is suitable for YOU.
Also, you should keep on posting just one problem per thread.
In general we do not give answers here. We provide help. So, ask for a hint on how to start solving the problem or show us your work up to the point where you got stuck or give us your answer and your work so we can check it. Understand the idea?
OK That is a good question you asked.
The first step in answering this question is to calculate EXACT answers. Can you do that? What are they?
The simplest and most common way to do rounding is (or used to be) called half adjusting. Let's take an example. Suppose your exact answer is
$43.66666666.
Step 1: Ignore everything past the THIRD decimal.
$43.666
Step 2: Add .005
$43.666 + 0.005 = 43.671.
Step 3: Ignore everything past the SECOND decimal.
$43.67 is your answer ROUNDED to the nearest cent.
An equivalent way to do this is to look at the third decimal. If it is 5 or larger, add 1 to the second decimal and throw away the decimals past the second. If the third decimal is smaller than 5, do nothing to the second decimal and throw away the decimals past the third. You get to the same place, but the process outlined above sort of explains what you are really doing.
Now do that with your answers. What do you get?
ok so $32.17 exactly is $38.30 for the 15% tip and $6.43 for the 20% tip
right?
