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Science Forum Index » Mathematics Forum » Discrete math
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| josmatt.joseph@gmail.com |
 Posted: Sat Apr 26, 2008 7:15 am |
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Can anybody help me with this with explanation.
A denotes the set of all persons watching foot ball, B denotes the set
of all persons
watching hockey and C set of all persons watching basket ball,
where the universal
set consists of 500 persons
│A │ = 285 │B│ = 195 │C│ = 115
│A ∩ C │= 45 │A ∩ B│ = 70 │B ∩ C│= 50 │A ∩ B ∩ C │C = 50
(a) Find how many watch all the games (b) How many watch exactly
one game ? |
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| Rob Johnson |
| Posted: Sat Apr 26, 2008 1:02 pm |
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In article <891ac373-9390-49f8-a82d-8e25f3e24d3c@27g2000hsf.googlegroups.com>,
"josmatt.joseph@gmail.com" <josmatt.joseph@gmail.com> wrote:
Quote: Can anybody help me with this with explanation.
A denotes the set of all persons watching foot ball, B denotes the set
of all persons
watching hockey and C set of all persons watching basket ball,
where the universal
set consists of 500 persons
|A| = 285 |B| = 195 |C| = 115
|A & C| = 45 |A & B| = 70 |B & C| = 50 |A & B & C| = 50
(a) Find how many watch all the games (b) How many watch exactly
one game ?
How can |A & C| = 45 and |A & B & C| = 50 ? Usually subsets have
fewer elements than the original set; that is, we should have
|A & B & C| <= |A & C|
When the numbers make sense, you can use the generalized
inclusion-exclusion principle to answer questions of this sort.
See <http://www.whim.org/nebula/math/counting.html>.
Rob Johnson <rob@trash.whim.org>
take out the trash before replying
to view any ASCII art, display article in a monospaced font |
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