2025 SST PRELIMS P1 Q17

2025 SST PRELIMS P1 Q17

Secondary 4
5 marks

A nonagon has six interior angles of \(x^\circ\) and three interior angles of \(y^\circ\).

  1. State the number of lines of symmetry if \(x\ne y\).[1]
  2. Find the sum of the interior angles of the nonagon.[1]
  3. Hence, show that \(y=-2x+420\).[1]
  4. Given that \(x:y=13:16\), find \(x\).[2]

Solution:

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Answer:(a) \(3\) (b) \(1260^\circ\) (c) shown (d) \(x=130\)

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