Lamp posts stand in a single straight line along a road, 40 m apart. One lamp post is 9th from the east end and 16th from the west end of the line. What is the distance between the first and the last lamp post of the line?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 920 m
The lamp post is counted from both ends, so posts in the line = 9 + 16 − 1. Between n posts in a line there are n − 1 gaps.
Posts in the line \(=9+16-1=24\)
Gaps between the first and the last post \(=24-1=23\)
Distance \(=23\times40=920\,\mathrm{m}\)
