The sum of the three lengths rounded to the nearest yard is ...
... 2 yd + 15 yd + 1 yd = 18 yd
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<em>Comment on this result</em>
In this case, this also happens to be the rounded value of the actual sum (17.94 yd ⇒ 18 yd). Sometimes, rounding the addends results in an error in the total, because rounding can introduce a bias if the numbers are not uniformly distributed.