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Question

Let N be the greatest number that will divide 600, 631 and 724, leaving the same remainder. What is the value of N ?

This question was previously asked in
CDS 2 2026 Maths Question Paper (13-Sep-2026)
The correct answer is

31

Greatest Number Problem Explained

The question asks for the greatest number, denoted as N, that divides 600, 631, and 724, ensuring the remainder is identical for each division.

Number N Differences Method

A key principle states that if a number N divides multiple numbers (say A, B, C) leaving the same remainder, then N must perfectly divide the differences between these numbers (A-B, B-C, A-C). We first calculate these differences:

  • Difference between 631 and 600: \(631 - 600 = 31\)
  • Difference between 724 and 631: \(724 - 631 = 93\)
  • Difference between 724 and 600: \(724 - 600 = 124\)

HCF Calculation for N

The greatest number N we are looking for is the Highest Common Factor (HCF) of these calculated differences: \(31\), \(93\), and \(124\).

To find the HCF, we list the prime factors for each difference:

  • Factors of \(31\): \(31\) (as it's a prime number)
  • Factors of \(93\): \(3 \times 31\)
  • Factors of \(124\): \(2 \times 2 \times 31\), which simplifies to \(4 \times 31\)

By comparing the factors, we see that \(31\) is the only common factor present in all three numbers. Therefore, the HCF(\(31\), \(93\), \(124\)) is \(31\).

Value of N Determined

The HCF represents the greatest number N that satisfies the condition.

Thus, the value of N is \(31\).

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Similar Questions

  1. If HCF of 768 and \(x^6y^2\) is \(32xy\) for natural numbers \(x \ge 2, y \ge 2\), then what is the value of \((x + y)\)?
  2. What is the HCF of \(2^{36}-1\) and \(2^{45}-1\)?
  3. The HCF of \(x\) and \(y\) is \(H\). Consider the following statements in respect of the HCF of \(p=\frac{x^3 + y^3}{x^2-xy+y^2}\) and \(q=\frac{x^3-y^3}{x^2+xy+y^2}\) : 

    I. The HCF of \(p\) and \(q\) can be \(H\). 

    II. The HCF of \(p\) and \(q\) can be \(2H\). 

    Which of the statements given above is/are correct?

  4. What is the HCF of \(x^3 + y^3 + 3xy-1\) and \((x + y)^2 - 1\)?
  5. A number N is such that when divided by 4, 6, 7 or 9, it leaves 3 as remainder. What is the smallest 4-digit number that satisfies this property?
  6. A plank of wood 4·25 m long and 3·4 m wide is to be cut into square pieces of equal size. How many square pieces of largest size can be cut from the plank, if no wastage is allowed ?
  7. What is the HCF of \(x^4 - 13x^2y^2 - 300y^4\), \(x^3 - 4x^2y - 4xy^2 - 5y^3\) and \(x^3 - 125y^3\)?
  8. Let \(N\) be a 5-digit number. When \(N\) is divided by 6, 12, 15, 24 it leaves respectively 2, 8, 11, 20 as remainders. What is the greatest value of \(N\)?
  9. Let \(N\) be the least positive multiple of 11 that leaves a remainder of 5 when divided by 6, 12, 15, 18. Which one of he following is correct?

  10. Let \(n\) be a natural number. The HCF of \(n, n + 10\) is 10. If the LCM is \(x\) (a 2-digit number), then how many values of \(x\) are possible?


Important Questions from LCM and HCF

  1. The HCF and LCM of two numbers are 12 and 72, respectively. If the ratio of the two numbers is 2 ∶ 3, then the larger of the two numbers is:

  2. Find the greatest number that will divide 43, 91 and 183 so as to leave the same remainder in each case.

  3. Joseph visits the club on every 5 th day, Harsh visits on every 24 th day, while Sumit visits on every 9 th day. If all three of them met at the club on a Sunday, then on which day will all three of them meet again?

  4. What is the least number which when divided by 12,20 and 24 leaves in each case a remainder of 8?

  5. Which of the following is a pair of co-primes?

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