Rounded to nearest..

[GMatTaker]

Just a general question on rounding. This is the basis of a question in OG 11 - PS, which I
wont repeat here.

If a person drives a car 490 miles and that figure is rounded to the
nearest 10 miles, the actual number of miles driven would be: ?

I thought the range of numbers would be 485 to 494 (inclusive).
The book seemed to indicate it is 484 to 495. What am i doing
wrong?

thank you.

[esledge]

Your thinking is basically correct. Without reading the OG explanation, I can only speculate, but it is possible you are getting hung up on the integers at the end of the range, and whether they are included or excluded.

When rounding to the nearest ten, you look only at the digit after--the units digit. If the units digit is 5 or greater, round up. If the units digit is 4 or less, round down (i.e. simply replace the units digit with zero).

Thus,
484 rounds down to 480.
484.99999 rounds down to 480
(Note: solely based on the 4 in the units digit, and ignoring the digits after the decimal--it's irrelevant that this number is actually very close to 485. That is, don't first round to 485 and then to 490.)
485 rounds up to 490.
486 rounds up to 490.
...and so on....
494 rounds down to 490.
494.99999 rounds down to 490.
(Again, solely based on the 4 in the units digit, and ignoring the digits after the decimal--it's irrelevant that this number is actually very close to 495. That is, don't first round to 495 and then to 500.)
495 rounds up to 500.

When rounded to the nearest 10, values in the range 485 <= x < 495 will round to 490. In words, that is the range from 485 (inclusive) to 495 (exclusive).

You might find this related thread interesting:
http://www.manhattangmat.com/forums/rou ... t3691.html