Earlier today I set four engineering puzzles. Here they are again with solutions. (Do check out the hundreds of great comments posted below the line in the original story.)
Alex Bellos is a Puzzle Setter at Yahoo News UK. He has been setting a puzzle every two weeks since 2015, exploring themes in science, education, and the natural sciences, with a focus on topics such as physics, biology, and astronomy. Alex's work has been featured in notable publications including Yahoo News, The Guardian, and Atlas Obscura.