Logic to Algorithm
Here is a question in Edmonotn Grandview Height School for Grade 8 students: A and B are two runners, A's speed is 15km/h, B's speed is 20km/h. 1 hour after A ran, B started to run to catch up A. How long would take B to catch up A? This is probably a simple math question for element school kids in China. I, totally trained in Chinese thinking, will get answer by doing (1*15)/(20-15) = 3 hrs. If we want to do the X way, so we can solve the problem as the following, which is taught in Math Power book: 1.let x be the time for B to catch up A 2.then by the time A catches B, A's total running time would be x+1 3.when A catchs B, their running distances are equal, so the following equation wil be used to solve the problem: 15(x+1) = 20x -> x = 3 hrs, same answer. But the school math teacher's solution is as the following: (of course it's right!) 1. let x be the A's running time (why not be B's time?!) 2. let's think about nagative, since time is passed! 3.