Some of the parts shown below make a complete square when they are fitted together. Which set of parts does this? (Parts may be turned round.)
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (A), (B) and (D) only
Parts form a complete square only if, placed side by side, they fill the square exactly, with no gap and no overlap. (A), (B) and (D) fill a 4 × 4 square when (A) is turned through 90° anticlockwise, (B) is turned through 90° clockwise and (D) is turned through 90° clockwise.
Option (1) — Incorrect. (C) looks like (B) but has one small square more. Together (A), (B) and (C) cover 18 small squares, while the 4 × 4 square has 16, so they cannot make it; they cannot be fitted into any other complete square either.
Option (2) — Incorrect. (C) looks like (B) but has one small square more. Together (B), (C) and (D) cover 15 small squares, while the 4 × 4 square has 16, so they cannot make it; they cannot be fitted into any other complete square either.
Option (4) — Incorrect. (C) looks like (B) but has one small square more. Together (A), (C) and (D) cover 17 small squares, while the 4 × 4 square has 16, so they cannot make it; they cannot be fitted into any other complete square either.