In a particular state, 70% of the counties received some rain on Monday, and 50% of the counties received some rain on Tuesday. No rain fell either day in 20% of the counties in the state. What percent of the counties received some rain on Monday and Tuesday?  Choose the correct choice:  A) 20 %  B) 40 %  C) 50 %  D) 60 %  E) 70 %

Rationale: "70 + 50 + 20 = 140 % the number is 40 % above 100 % because 40 % of the counties were counted twice . the answer is b ."
Answer: B