Andy estimated that he would need 77 feet of lumber for a tree house project. he later found that the actual amount of lumber needed was 66 feet. what was the percent error of andy's estimation?

It makes a difference how you interpret this question. He needed 66 feet of lumber. That is the key number that you have to use. He had (77 - 66) = 11 feet of lumber too much.

% error = (11/66) * 100 = 16.7% error.<<< Answer

agree

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