Word Ladder: Tool to Book
Read the puzzle
A word ladder climbs from TOOL at the bottom to BOOK at the top, changing one letter at each step: TOOL, COOL, ?, HOOK, BOOK. Which word fills the gap: COOK, POOL, LOOK or CORK?
Which word fills the gap?
It must differ by one letter from COOL and from HOOK.
COOK
COOL to COOK changes L to K; COOK to HOOK changes C to H.
How to solve it
Step one: the missing word must be one letter away from the word below it, COOL, and one letter away from the word above it, HOOK.
Step two: compare COOL and HOOK. They share the two O's in the middle, and differ at the start, C against H, and at the end, L against K. Two letters must change, so the gap word must change one of them and keep the other.
Step three: test the two possible middle words. Changing the end first gives COOK, which is a real word. Changing the start first gives HOOL, which is not. So the gap is COOK: COOL to COOK swaps L for K, and COOK to HOOK swaps C for H.
Check the other choices. POOL is one step from COOL but two from HOOK. LOOK is one step from HOOK but two from COOL. CORK changes both an O and the L of COOL, so it is two steps from COOL, and it is two steps from HOOK as well.
The usual wrong answer is LOOK, because it rhymes with HOOK and BOOK and looks at home in the ladder. Always test both neighbours, not just the one above.
