<PRE><B>Question 1185764</B>
&lt;br&gt;
The sum of the lengths of the supports is&lt;br&gt;
3+7+11+...+559+563+559+...+11+7+3&lt;br&gt;
= 2(3+7+11+...+559)+563&lt;br&gt;
Find the sum of the arithmetic sequence in parentheses using
sum = number of terms times average of all the terms, or
sum = number of terms times average of first and last terms.&lt;br&gt;
The number of terms is (last minus first) divided by common difference, plus 1.&lt;br&gt;
(559-3)/4+1 = 139+1 = 140&lt;br&gt;
The average of the first and last terms is (3+559)/2 = 281.&lt;br&gt;
The sum of the lengths of the supports is then&lt;br&gt;
2(140*281)+563&lt;br&gt;
Use a calculator to get&lt;br&gt;
ANSWER: 79,243 feet&lt;br&gt;
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