Machine A produces 100 parts twice as fast as Machine B does. Machine B produces 100 parts in 40 minutes. If each machine produces parts at a constant rate, how many parts does Machine A produce in 10 minutes? Choices: A) 20 B) 50 C) 60 D) 40 E) 30

Rationale: "machine b produces 100 part in 40 minutes . machine a produces 100 parts twice as fast as b , so machine a produces 100 parts in 40 / 2 = 20 minutes . now , machine a produces 100 parts in 20 minutes which is 100 / 20 = 5 parts / minute . 5 parts x a total of 10 minutes = 50 b"
Answer: B