The measure of seven of the angles in an octagon add up to 945. What is the measure of the 8th angle?

Answer 1

For a polygon with n sides, the formula for the sum of the interior angles is (n-2)·180°. An octagon has 8 sides so n = 8. Plug n = 8 into the formula to compute the sum of all the internal angles. You know 7 of the 8 angles add up to 945°, so subtract 945° from the total to get the measure of the 8th angle.