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OG - PS - #129

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Luci
 Post subject: OG - PS - #129
 Post Posted: Fri Jul 20, 2007 12:51 pm 
I have a doubt with rounding

EX: If we have 19.4 and we want to round to the units we´ll get 19, right?

But if we have 19.6 and we round to the units we´ll get 20.

And what do we get if we round 19.5? I think is 19 but not sure.

Am I right or wrong?

I´m having this doubt because of problem 129 PS OG11. In this problem they round 284 miles to the nearest 10 miles and they said the rounding is 290 miles. Shouldn´t it be 280 miles?

Thanks!!
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JadranLee
 Post subject:
 Post Posted: Fri Jul 20, 2007 5:43 pm 
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ManhattanGMAT Staff


Posts: 108
Location: Chicago, IL
When rounding numbers, all you need to do is look at the digit immediately to the right of the digit you are rounding to. If that digit on the right is 5,6,7,8, or 9, round up. If it's 0,1,2,3, or 4, round down.

Thus 19.5 rounded to the nearest units digit is 20.

Likewise, 284 miles rounded to the nearest 10 miles is 280 miles. (My copy of the OG11th edition doesn't say it's 290 - maybe your copy has some sort of misprint.)

Interestingly, there is a slight imprecision in the way the book explains PS129 on p. 227. They say that if x miles, when rounded to the nearest 10 miles, is 280, then x can "range anywhere from 285 to 295 miles". A more precise way of saying this would be "285 is less than or equal to x, which is less than 295", because 295 actually would round up to 300. There is a similar imprecision in what they say about rounding gallons of gas.

-Jad
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