Ann is organizing a two day workshop next month. Exactly 100 people will be attending either one day kje the workshop or both. Out of them, 70% will be there for the first day, and 80% for the second. Help Ann calculate how many people will be present for both days of the workshop?  Choose the correct choice from the following choices
A) 30
B) 40
C) 50
D) 60
E) 70
The total number of people attending the workshop is n = 100.   The number of people attending the first day of the workshop is 70% of it, thus   n (A)=70/100×100=70.   The number of people attending the second day of the workshop is 80%, thus   n (B)=80/100×100=80.   In order to calculate the number of people attending both days of the workshop we can use the following equation:   n (AnB)=n (A)+n (B) -n = 70+80-100=150-100= 
<gadget id="calculator">150-100</gadget>
<output>50</output>
50   So, 50 people will be attending both the first and the second day of Ann's workshop.   ANSWER: 50
<result>C</result>
Ann is organizing a two day workshop next month. Exactly 100 people will be attending either one day kje the workshop or both. Out of them, 70% will be there for the first day, and 80% for the second. Help Ann calculate how many people will be present for both days of the workshop?