I think I know exactly what the mistakes are! The 42% should
be 32% and the 23% should be 13%.
In a town 85% of the people speak English, 40% speak kannada
and 20% speak Hindi, also speak English and Kannada,
speak kannada and Hindi. And 10% speak English and Hindi.
Find the percentage of people who can speak all the three languages?
Everybody in circle E speaks English.
Everybody in circle K speaks Kannada.
Everybody in circle H speaks Hindi.
If the little letters represent the percentages in
each of the 7 regions, then
p+q+r+s+t+u+v = 100%. Let's not bother
with the percent marks:
p+q+r+s+t+u+v = 100
In a town 85% of the people speak English,
p+q+s+t = 85
40% speak kannada
q+r+t+u = 40
and 20% speak Hindi,
s+t+u+v = 20
also speak English and Kannada,
q+t = 32
speak kannada and Hindi.
t+u = 13
And 10% speak English and Hindi.
s+t = 10
Find the percentage of people who can speak all the three languages?
So we want the value of t.
The 7 equations in 7 unknowns are
1. p+q+r+s+t+u+v = 100
2. p+q+ s+t = 85
3. q+r +t+u = 40
4. s+t+u+v = 20
5. q +t = 32
6. t+u = 13
7. s+t = 10
Let's get all the other 6 letters
in terms of t:
From 7,
8. s = 10-t
From 5,
9. q = 32-t
From 2,
p+32-t+10-t+t = 85
p-t+42 = 85
10. p = 43+t
From 6,
11. u = 13-t
8. s = 10-t
From 4,
10-t+t+13-t+v = 20
23-t+v = 20
12. v = t-3
9. q = 32-t
11. u = 13-t
From 3,
32-t+r+t+13-t = 40
r-t+45 = 40
13. r = t-5
Now that we have all the other 6 letters in terms of t,
we can substitute into 1:
1. p+q+r+s+t+u+v = 100
43+t+32-t+t-5+10-t+t+13-t+t-3 = 100
90+t = 100
t = 10
That's the answer. But let's fill in the Venn diagram:
p = 43+t = 43+10 = 53
q = 32-t = 32-10 = 22
r = t-5 = 10-5 = 5
s = 10-t = 10-10 = 0
t = 10
u = 13-t = 3
v = t-3 = 10-3 = 7
So the Venn diagram is:
Edwin