SOLUTION: 50 students in a class 18 studying biology 30 chemistry 25 physics 11 studing physics and chemistry 9 biology and chemistry 7 biology and physics. How many students are st

Question 971208: 50 students in a class
18 studying biology
30 chemistry
25 physics
11 studing physics and chemistry
9 biology and chemistry
7 biology and physics.
How many students are studying all three subs ??
Answer by khai(18) (Show Source): You can put this solution on YOUR website!
I suggest to draw the Venn diagram first because it will make you more make sense.
ok.. so,
18 studying biology; 9 biology and chemistry; 7biology and physic.
18 - (9+7) = 2 (2 is the student who only study bio)
30 chemistry; 9 biology and chemistry; 11 studying physics and chemistry
30 - (11+9) = 10 (only chemistry)
25 physics; 7 biology and physics; 11 studying physics and chemistry
25 - (7+11) = 7 (only physic)
add all numbers and subtract from 50 because it said 50 students in a class
50 - (2+10+7+9+7+11) = 4

the answer is 4 students are studying all three subs......
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