I just have some niggling doubts on solving these problems. I'm aware of the method of 'picking numbers', but I seek a more general understanding. Could someone explain to me how to solve these problems generally? Or how to think of them.
1.) Bill has to type a paper that is pages long, with each page containing words. If Bill types an average of words per minute, how many hours will it take him to finish the paper?
2.) If David paints at the rate of houses per day, how many houses does he paint in days, in terms of and ?