Question:

In an examination, 62% of the candidates failed in English, 42% in Mathematics and 20% in both. The number of those who passed in both the subjects is: 
 

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Use the principle of inclusion-exclusion to find the percentage of candidates who failed in either English or Mathematics or both.
Updated On: May 21, 2025
  • 11
  • 16
  • 18
  • None of these
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The Correct Option is B

Approach Solution - 1

Step 1: Calculate the percentage of candidates who failed in either English or Mathematics or both
Percentage failed in English or Mathematics or both = Percentage failed in English + Percentage failed in Mathematics - Percentage failed in both = 62% + 42% - 20% = 84% 
Step 2: Calculate the percentage of candidates who passed in both subjects
Percentage passed in both subjects = 100% - Percentage failed in English or Mathematics or both = 100% - 84% = 16% 
Step 3: Assume the total number of candidates
Let the total number of candidates be \( x \). 
Step 4: Calculate the number of candidates who passed in both subjects
Number of candidates who passed in both subjects = 16% of \( x \) = \( \frac{16}{100} \times x \) 
Step 5: Relate the number to the options
Since the options are whole numbers, we can assume \( x = 100 \) for simplicity. Then, the number of candidates who passed in both subjects = \( \frac{16}{100} \times 100 = 16 \).
 

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Approach Solution -2

Step 1: Given Information
We are given the following percentages: - 62% of the candidates failed in English. - 42% of the candidates failed in Mathematics. - 20% of the candidates failed in both English and Mathematics. We need to find the number of candidates who passed in both subjects.

Step 2: Total Percentage of Candidates
Let the total number of candidates be \( 100 \) (as percentages are given). Therefore, we can represent the following: - 62% failed in English, so 38% passed in English. - 42% failed in Mathematics, so 58% passed in Mathematics. - 20% failed in both subjects, meaning those candidates are included in both the English and Mathematics failure percentages. Now, let's use the principle of inclusion-exclusion to calculate the percentage of candidates who passed in both subjects.

Step 3: Calculate Candidates Passing in Both Subjects
Let: - \( A \) be the set of candidates who failed in English. - \( B \) be the set of candidates who failed in Mathematics. We are given: - \( |A| = 62\% \), - \( |B| = 42\% \), - \( |A \cap B| = 20\% \) (candidates who failed in both subjects). The percentage of candidates who failed in at least one subject is: \[ |A \cup B| = |A| + |B| - |A \cap B| = 62\% + 42\% - 20\% = 84\%. \] Thus, 84% of candidates failed in at least one subject. Therefore, the percentage of candidates who passed in both subjects is: \[ 100\% - 84\% = 16\%. \]

Step 4: Conclusion
The percentage of candidates who passed in both English and Mathematics is 16%.

The correct answer is: 16%

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