UPSC Prelims 2016·CSAT·Quantitative Aptitude·Arithmetic

In aid of charity, every student in a class contributes as many rupees as the number of students in that class. With the additional contribution of Rs. 2 by one student only, the total collection is Rs. 443. Then how many students are there in the class?

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Last updated 23 May 2026, 3:31 pm IST
  1. A12
  2. B21Correct
  3. C43
  4. D45

Explanation

To find the number of students, let the total number of students in the class be x. According to the problem, each student contributes as many rupees as the number of students. Therefore, the total contribution from all students is x multiplied by x, which is x squared. One student contributes an additional 2 rupees. So, the total collection becomes x squared plus 2. We are given that the total collection is 443 rupees. This gives us the equation: x squared plus 2 equals 443. Subtracting 2 from both sides, we get x squared equals 441. To find x, we take the square root of 441. Since 20 times 20 is 400 and 21 times 21 is 441, x equals 21. Therefore, there are 21 students in the class. The correct option is B.
Quantitative Aptitude: In aid of charity, every student in a class contributes as many rupees as the number of students in that class. With the

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