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Question

A survey of 450 students about their subjects of interest resulted in the following outcome.
  • 150 students are interested in Mathematics.
  • 200 students are interested in Physics.
  • 175 students are interested in Chemistry.
  • 50 students are interested in Mathematics and Physics.
  • 60 students are interested in Physics and Chemistry.
  • 40 students are interested in Mathematics and Chemistry.
  • 30 students are interested in Mathematics, Physics and Chemistry.
  • Remaining students are interested in Humanities.
Based on the above information, the number of students interested in Humanities is

The correct answer is
45

Calculating Humanities Interest Using Set Theory

This problem involves finding the number of students interested in Humanities, which represents the students outside the sets of Mathematics, Physics, and Chemistry interests. We use the Principle of Inclusion-Exclusion.

Given Information

  • Total students: 450
  • Mathematics (M): 150
  • Physics (P): 200
  • Chemistry (C): 175
  • Mathematics and Physics ($M \cap P$): 50
  • Physics and Chemistry ($P \cap C$): 60
  • Mathematics and Chemistry ($M \cap C$): 40
  • Mathematics, Physics, and Chemistry ($M \cap P \cap C$): 30

Applying Inclusion-Exclusion Principle

First, calculate the total number of students interested in at least one of Mathematics, Physics, or Chemistry ($|M \cup P \cup C|$).

The formula is:

$|M \cup P \cup C| = |M| + |P| + |C| - (|M \cap P| + |P \cap C| + |M \cap C|) + |M \cap P \cap C|$

Substitute the given values:

$|M \cup P \cup C| = 150 + 200 + 175 - (50 + 60 + 40) + 30$ $|M \cup P \cup C| = 525 - (150) + 30$ $|M \cup P \cup C| = 525 - 150 + 30$ $|M \cup P \cup C| = 375 + 30$ $|M \cup P \cup C| = 405$

So, 405 students are interested in at least one of the three subjects (Mathematics, Physics, or Chemistry).

Determining Humanities Interest

The students interested in Humanities are those remaining students who are not interested in Mathematics, Physics, or Chemistry.

Number of Humanities students = Total students - $|M \cup P \cup C|$

$ \text{Humanities} = 450 - 405 $ $ \text{Humanities} = 45 $

Therefore, 45 students are interested in Humanities.

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Important Questions from Numerical Reasoning

  1. Let $p_1$ and $p_2$ denote two arbitrary prime numbers. Which one of the following statements is correct for all values of $p_1$ and $p_2$?
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  4. In a zoo, three lions and four tigers eat 390 kg of food every week. In another zoo, four lions and five tigers eat 500 kg of food every week. Lions and tigers eat different amounts of food, but all individuals of the same species eat the same amount. The amount of food a single lion eats per week is ________ kg.
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    Which one of the following options is CORRECT?

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