Round to the nearest three decimal

30.458

r=0.7589

Question

Round to the nearest three decimal

30.458

r=0.7589

talentedgirl · Answer

30.4
and 
758 I think

talentedgirl · Answer

@mrm

mrm · Answer

Hi talented.  I'm not sure I understand your problem.  Do you only need to round those two numbers, or is there more to the problem?

talentedgirl · Answer

Round these answers to the nearest  decimals

talentedgirl · Answer

3 decimals

mrm · Answer

The number of decimal places is the number of digits after the decimal dot.
30.458 is already at 3 decimal places.  

r=0.7589 is written to 4 decimal places.  So we can round this one.  Give it a try.

talentedgirl · Answer

.758

mrm · Answer

Not quite. In order to round 0.7589 to 3 decimal places, we need to look at the 3rd digit and the digit to the right of it.

So if we count three places over we get the digit 8.  Now look at the digit to the right of it: 9.  

The rules of rounding are to the 3rd decimal place are:
- if the number to the right of our 3rd digit is 5 or more, we add one to the 3rd digit, and drop the rest
- if the number to the right of our 3rd digit is 4 or less, we leave it alone, and then drop the rest.

For example lets round 0.65478 to the 3rd decimal place:

Our 3rd digit is 4, and the number to the right is 7.
By the rules of rounding, we add 1 to 4, and then drop the rest of the digits.
So then we are left with:  0.655, which is 0.6547 rounded to the 3rd decimal place.

talentedgirl · Answer

30.458  The 0  is then a 1

talentedgirl · Answer

Or do you only do that to the numbers after the decimal sign?

mrm · Answer

No.  You are rounding to the 3rd decimal place, which means that your number will have 3 digits after the decimal point when you are done rounded.  30.458 already has 3 digits after the decimal point: .458 

So, 30.458 rounded to the 3rd decimal places is just 30.458

talentedgirl · Answer

Oh,I thought that mean there could only be 3 numbers

mrm · Answer

Nope, only 3 numbers after the decimal point!

mrm · Answer

You could have 10234923465456.674567563456 rounded to the 3rd decimal place and it would be:

10234923465456.675

talentedgirl · Answer

I see

mrm · Answer

So 0.7589 rounded to the 3rd decimal place would be 0.759

talentedgirl · Answer

No 8

talentedgirl · Answer

Thank you

mrm · Answer

No, you are either rounding the 8 up or down, depending on the value of the next digit.  Since 0.7589 is closer to 0.7590 than 0.7580... we choose 0.759