A college awarded $38$ medals in football, $15$ in basketball and $20$ in cricket. If these medals went to a total of $58$ men and only three men got medals in all the three sports, how many received medals in exactly two of the three sports?
Let $F, B$ and $C$ denote the set of men who received medals in football, basketball and cricket. respectively.
Then $n( F )=38, n( B )=15, n( C )=20$
$n( F \cup B \cup C )=58$ and $n( F \cap B \cap C )=3$
Therefore, $\quad n( F \cup B \cup C )=n( F )+n( B )$
$+n( C )-n( F \cap B )-n( F \cap C )-n( B \cap C )+$
$n( F \cap B \cap C )$
gives $n( F \cap B )+n( F \cap C )+n( B \cap C )=18$
Consider the Venn diagram as given in Fig
Here, $a$ denotes the number of men who got medals in football and basketball only, $b$ denotes the number of men who got medals in football and cricket only, $c$ denotes the number of men who got medals in basket ball and cricket only and $d$ denotes the number of men who got medal in all the three.
Thus, $d=n( F \cap B \cap C )=3$ and $a+d+b+d+c+d=18$
Therefore $a+b+c=9,$
which is the number of people who got medals in exactly two of the three sports.
A market research group conducted a survey of $1000$ consumers and reported that $720$ consumers like product $\mathrm{A}$ and $450$ consumers like product $\mathrm{B}$, what is the least number that must have liked both products?
A group of $40$ students appeared in an examination of $3$ subjects - Mathematics, Physics Chemistry. It was found that all students passed in at least one of the subjects, $20$ students passed in Mathematics, $25$ students passed in Physics, $16$ students passed in Chemistry, at most $11$ students passed in both Mathematics and Physics, at most $15$ students passed in both Physics and Chemistry, at most $15$ students passed in both Mathematics and Chemistry. The maximum number of students passed in all the three subjects is___________.
In a survey of $60$ people, it was found that $25$ people read newspaper $H , 26$ read newspaper $T, 26$ read newspaper $I, 9$ read both $H$ and $I, 11$ read both $H$ and $T,$ $8$ read both $T$ and $1,3$ read all three newspapers. Find:
the number of people who read at least one of the newspapers.
In a certain town, $25\%$ of the families own a phone and $15\%$ own a car; $65\%$ families own neither a phone nor a car and $2,000$ families own both a car and a phone. Consider the following three statements
$(A)\,\,\,5\%$ families own both a car and a phone
$(B)\,\,\,35\%$ families own either a car or a phone
$(C)\,\,\,40,000$ families live in the town
Then,
In a school there are $20$ teachers who teach mathematics or physics. Of these, $12$ teach mathematics and $4$ teach both physics and mathematics. How many teach physics ?