Eric Nicholas K's answer to Amelia's Secondary 1 Maths Singapore question.

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Eric Nicholas K
Eric Nicholas K's answer
3831 answers (Tutor Details)
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Hi Amelia! Here are my workings for this question. Remember that the sum of all the exterior angles in a polygon is 360 deg.

The first two exterior angles have a value of 35 deg and 72 deg.

This means that the sum of the remaining (n - 2) exterior angles
= 360 - 35 - 72
= 325 - 72
= 253

The remaining exterior angles are 23 each, so the number of such exterior angles
= 253/23
= 11

Add this to the starting two exterior angles and we have the total number of sides of the polygon = 11 + 2 = 13 so n = 13.