How many straight lines are used in the figure below? (A straight line cut into pieces by other lines is still one line.)
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 12
Each full straight line counts once, however many pieces other lines cut it into. In the figure below every line is numbered; group them by direction.
Horizontal lines (4): 1, 2, 3, 4
Vertical lines (4): 5, 6, 7, 8
Slanting lines (4): 9, 10, 11, 12
Total \(=4+4+4=12\) straight lines.
Why the other options are incorrect
Option (1) 8 — Incorrect. This leaves out the 4 vertical lines.
Option (2) 13 — Incorrect. This counts one line twice; the groups above add up to 12.
Option (4) 16 — Incorrect. This counts every piece between two corners or crossings as a separate line.