Question:

In a class of $60$ students, $25$ students play cricket and $20$ students play tennis, and $10$ students play both the games. Then, the number of students who play neither is

Updated On: Sep 4, 2024
  • $0$
  • $25$
  • $35$
  • $45$
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The Correct Option is B

Solution and Explanation

Let student play cricket $=C$
Student play tennis $=T$
and total number of students $=S$
$\therefore n(S) =60, n(C)=25,\, n(T)=20$
and $n(C \cap T) =10$
Now, $n(C \cup T) =n(C)+n(T)-n(C \cap T)$
$=25+20-10=35$
$\therefore$ The number of students who play neither game
$=n(C \cap T)'=n(S)-n(C \cup T)$
$=60-35=25$
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Concepts Used:

Sets

Set is the collection of well defined objects. Sets are represented by capital letters, eg. A={}. Sets are composed of elements which could be numbers, letters, shapes, etc.

Example of set: Set of vowels A={a,e,i,o,u}

Representation of Sets

There are three basic notation or representation of sets are as follows:

Statement Form: The statement representation describes a statement to show what are the elements of a set.

  • For example, Set A is the list of the first five odd numbers.

Roster Form: The form in which elements are listed in set. Elements in the set is seperatrd by comma and enclosed within the curly braces.

  • For example represent the set of vowels in roster form.

A={a,e,i,o,u}

Set Builder Form: 

  1. The set builder representation has a certain rule or a statement that specifically describes the common feature of all the elements of a set.
  2. The set builder form uses a vertical bar in its representation, with a text describing the character of the elements of the set.
  3. For example, A = { k | k is an even number, k ≤ 20}. The statement says, all the elements of set A are even numbers that are less than or equal to 20.
  4. Sometimes a ":" is used in the place of the "|".