i tried a triple venn diagram but not really cooperating. WHat is an easy method?
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Appetite for 700 and I scraped my plate!
Don't give up on Venn diagrams. I've attached mine to show you what my approach is.
Without using "%" everywhere, I expressed the following equations:
100 = (S + M + B) + (x + y + 30) - 2(m) ............. Eq 1
Where
S + M + B = Pple who only study one subject
x + y + 30 = Pple who study two or more subjects
m = Pple who study all three subjects (NOTE: Need to subtract 2(m) from Eq 1 because it is over-counted in [x + y + 30])
Also,
56 = S + x + 30 - m............. Eq 2
44 = M + 30 + y - m............. Eq 3
40 = B + x + y - m............... Eq 4
Add up Equations 2, 3 & 4, you get:
140 = S + M + B + 2(x + y + 30) - 3m............. Eq 5
Combine Eq 1 and 5 by substraction: (Eq 5)- (Eq 1)
40 = x + y + 30 - m
(x + y - m) = 10
Since we're trying to isolate B, substitute x + y - m = 10 into Eq 4, which gives you 30.
Remember 30 is the percentage of total students, so 30% of 400 = 120.
