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?  Answers
A) 20%  B) 40%  C) 50%  D) 60%  E) 70%
70 + 50 + 20= 
<gadget id="calculator">70 + 50 + 20</gadget>
<output>140</output>
140%   The number is 40% above 100% because 40% of the counties were counted twice.   The answer is 40%.
<result>B</result>
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?