Question:

Out of $100$ students; $15$ passed in English, $12$ passed in Mathematics, $8$ in Science, $6$ in English and Mathematics, $7$ in Mathematics and Science, $4$ in English and Science; $4$ in all the three passed. Then (i) The number of students passed in English and Mathematics but not in Science is (ii) The number of students only passed in Mathematics is (iii) The number of students passed in more than one subject is

Updated On: Jul 6, 2022
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  • b
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  • d
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The Correct Option is B

Solution and Explanation

Let $U$, $E$, $M$ and $S$ be denote the total number of students, number of students passed in English, Mathematics and Science, respectively. Here, $n(U) = 100$, $n(E) = 15$, $n(M) = 12$, $n(S) = 8$, $n(E \cap M) = 6$, $n(M \cap S) = 7$, $n(E \cap S) = 4$ and $n (E \cap M \cap S) = 4$ (i) $\therefore$ The number of students passed in English and Mathematics but not in Science $= n ( E \cap M \cap \bar{S})$ $= n(E \cap M) - n(E \cap M \cap S) = 6 - 4 = 2$ (ii) The number of students only passed in Mathematics $= n(M \cap \bar{E} \cap \bar{S})$ $= n(M) - n(M \cap E) - n(M \cap S) + n(M \cap E \cap S)$ $= 1 2 -6 -7 + 4 = 16-13 = 3$ (iii) The number of students passed in more than one subject $= n(M \cap E) + n(M \cap S ) + n(S \cap E) - 2n(M \cap E \cap S)$ $= 6 + 7 + 4 - 2(4) = 17-8 = 9$
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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 "|".