If there are 200 questions in a 3 hr examination. Among these questions are 50 type A problems, which requires twice as much as time be spent than the rest of the type B problems. How many minutes should be spent on type A problems?
Choose the correct answer
A) 72 min B) 62 min C) 70 min D) 74 min E) 76 min

Rationale: "x = time for type b prolems 2 x = time for type a problem total time = 3 hrs = 180 min 150 x + 50 * 2 x = 180 x = 180 / 250 x = 0.72 time taken for type a problem = 50 * 2 * 0.72 = 72 min answer : a"
Answer: A