Question 1139806
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If you make a sketch in the piece of paper, you will see a right-angled triangle.


Do you know what a "right-angled triangle" means ?


OK, very good.


Next question: do you know what the Pythagorean theorem is ?


OK, very good.  Then apply it.  You will get


b = {{{sqrt(8^2-6^2)}}} = {{{sqrt(64-36)}}} = {{{sqrt(28)}}} = 5.29 miles (rounded as requested).   <U>ANSWER</U>
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Solved.