In a survey of 220 students of a higher secondary school, it was found that at least 125 and at most 130 students studied Mathematics; at least 85 and at most 95 studied Physics; at least 75 and at most 90 studied Chemistry; 30 studied both Physics and Chemistry; 50 studied both Chemistry and Mathematics; 40 studied both Mathematics and Physics and 10 studied none of these subjects. Let m and n respectively be the least and the most number of students who studied all the three subjects. Then m+n is equal to .
Answer
45
Solution
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Let x = number who studied all three
n(M )=220-10=210
210=n(M)+n(P)+n(C)-(40+30+50)+x
n(M)+n(P)+n(C)=330-x
125+85+75 n(M)+n(P)+n(C) 130+95+90
285 330-x 315 15 x 45
Also Physics and Chemistry only =30-x 0 x 30
15 x 30 m=15, n=30 m+n=45
Answer: 45