JAMB 1991 · UME · Q34

If the exterior angles of a pentagon are $x^\circ$ , $(x + 5)^\circ$ , $(x + 10)^\circ$ , $(x + 15)^\circ$ and $(x + 20)^\circ$ , find $x$ .

Worked solution (try it first)

The exterior angles of any polygon add up to $360^\circ$ : $x + (x + 5) + (x + 10) + (x + 15) + (x + 20) = 360$ .
Collect terms: $5x + 50 = 360$ , so $5x = 310$ .
Divide by 5: $x = 62$ , option C.