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?
Let $U$ be the set of consumers questioned, $S$ be the set of consumers who liked the product $A$ and $T$ be the set of consumers who like the product $B.$ Given that
$n( U )=1000, n( S )=720, n( T )=450$
So $ n( S \cup T ) =n( S )+n( T )-n( S \cap T ) $
$=720+450-n( S \cap T )=1170-n( S \cap T ) $
Therefore, $n( S \cup T )$ is maximum when $n( S \cap T )$ is least.
But $S \cup T \subset U$ implies $n( S \cup T ) \leq n( U )=1000 .$
So, maximum values of $n( S \cup T )$ is $1000 .$
Thus, the least value of $n( S \cap T )$ is $170 .$
Hence, the least number of consumers who liked both products is $170$
In a survey of $220$ students of a higher secondary school, it was found that at least $125$ and at most $130$ students studied Mathematics; at least $85$ and at most $95$ studied Physics; at least $75$ and at most $90$ studied Chemistry; $30$ studied both Physics and Chemistry; $50$ studied both Chemistry and Mathematics; $40$ studied both Mathematics and Physics and $10$ studied none of these subjects. Let $\mathrm{m}$ and $\mathrm{n}$ respectively be the least and the most number of students who studied all the three subjects. Then $\mathrm{m}+\mathrm{n}$ is equal to .............................
In a group of $400$ people, $250$ can speak Hindi and $200$ can speak English. How many people can speak both Hindi and English?
Out of $800$ boys in a school, $224$ played cricket, $240$ played hockey and $336$ played basketball. Of the total, $64$ played both basketball and hockey; $80$ played cricket and basketball and $40$ played cricket and hockey; $24$ played all the three games. The number of boys who did not play any game is
In a survey of $600$ students in a school, $150$ students were found to be taking tea and $225$ taking coffee, $100$ were taking both tea and coffee. Find how many students were taking neither tea nor coffee?
A survey shows that $73 \%$ of the persons working in an office like coffee, whereas $65 \%$ like tea. If $x$ denotes the percentage of them, who like both coffee and tea, then $x$ cannot be