It’s time for math mania, and those who enjoy mental gymnastics will get a good workout with these puzzles. Begin with short and simple warm-ups: How long would it take 100 storks to catch 100 frogs when five storks need five minutes to catch five frogs? (The answer: Five minutes—it doesn’t matter whether there are one or one hundred storks, the time it takes for each stork to catch a frog is the same.) Move on to visual problems, games with sticks, and other feats of numerical magic.