James buys 2 puzzles that are 2000 pieces each. He anticipates for these larger puzzles he can do 100 pieces every 10 minutes. So how long would it take to finish both puzzles? Let's be accurate as possible.
His speed means he can do 10 / 100 = .1 minute per piece. So he can finish 1 puzzle in 2000 * .1 = 200 minutes. So these two puzzles take 200 * 2 = 400 minutes.
The answer: 400.