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 2
The correct answer is Option (2) → (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 3 × 3 square when (B) is turned through 90° anticlockwise and (D) is turned through 180°.
Option (1) — Incorrect. (C) looks like (B) but has one small square more. Together (A), (C) and (D) cover 10 small squares, while the 3 × 3 square has 9, so they cannot make it; they cannot be fitted into any other complete square either.
Option (3) — Incorrect. (C) looks like (B) but has one small square more. (A), (B) and (C) cover as many small squares as the 3 × 3 square, but they cannot be fitted into it, or into any complete square, without a gap or an overlap.
Option (4) — Incorrect. (C) looks like (B) but has one small square more. Together (B), (C) and (D) cover 11 small squares, while the 3 × 3 square has 9, so they cannot make it; they cannot be fitted into any other complete square either.