In a class 30 students play cricket, 40 students play football and 20 play none of the two games.
If there are 80 students exactly in the class, how many play exactly ONE of the two games?
Choices:
A) 40
B) 50
C) 80
D) 85
E) 90
n(C) = 30, n(F) = 40 and n(C' or F') = 20   =&gt; n(C or F) = 80 - 20= 
<gadget id="calculator">80 - 20</gadget>
<output>60</output>
60   also, n(C or F)= n(C) + n(F) - n(C and F)   =&gt; 60 = 30 + 40 - n(C and F)   i.e. n(C and F) = 10   so, 30 - 10 = 20 students play just football and 40 - 10= 
<gadget id="calculator">40 - 10</gadget>
<output>30</output>
30 students play just cricket=&gt; 20 + 30= 
<gadget id="calculator">20 + 30</gadget>
<output>50</output>
50 students play exactly ONE game   50)
<result>B</result>
In a class 30 students play cricket, 40 students play football and 20 play none of the two games.
If there are 80 students exactly in the class, how many play exactly ONE of the two games?