Question 1134540
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<pre>
There is a universal set U of 400 students.


There is a subset D of 250 students that have a dog.


There is a subset C of 190 students that have a cat.


And there is the intersection (D n C) of these subsets, which contains 160 students that have a dog <U>AND</U> a cat.


Then the number of students who have a dog <U>OR</U> a cat is  n(D U C) = n(D) + n(C) - n(D n C) = 250 + 190 - 160 = 280.


The answer to the first question is  P(D) = {{{n(D)/400}}} = {{{250/400}}} = {{{5/8}}}.


The answer to the second question is  P(D U C) = {{{n(d_U_C)/400}}} = {{{280/400}}} = {{{7/10}}}.
</pre>

Solved, answered and completed.


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If you want to learn more about the formula to calculate the union of subsets, look into my lesson

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/word/misc/Counting-elements-in-sub-sets-of-a-given-finite-set.lesson>Counting elements in sub-sets of a given finite set</A>

in this site.