Question:

Each student in a class of 40, studies at least one of the subjects English, Mathematics and Economics. 16 study English, 22 Economics and 26 Mathematics, 5 study English and Economics, 14 Mathematics and Economics and 2 study all the three subjects. The number of students who study English and Mathematics but not Economics is

Updated On: Jul 7, 2024
  • 7
  • 5
  • 10
  • 4
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The Correct Option is B

Solution and Explanation

C stands for set of students taking economics $a + b + c + d + e + f + g = 40; a + b + d + g = 16$ $b + c + e + g = 22; d + e + f + g = 26$ $b + g = 5; e + g = 14; g = 2$ Go by backward substitution $e = 12, b = 3, d + f = 12, c + e = 17 \Rightarrow c = 5;$ $a + d = 11$ $a +d + f = 18 \Rightarrow f = 7 \quad \therefore d = 12 - 7 = 5$
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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 "|".