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Question

Find the least number which when divided by 5, 6 and 7 leaves remainders 4, 5 and 6.

This question was previously asked in
RRB NTPC 2024 Undergraduate CBT 1 Question Paper (29-Aug-2025) (Shift 1)
The correct answer is
209

Let the number be \(x\).

According to the problem, when \(x\) is divided by 5, 6, and 7, the remainders are 4, 5, and 6 respectively. This can be expressed as:

  • \(x \equiv 4 \pmod{5}\)
  • \(x \equiv 5 \pmod{6}\)
  • \(x \equiv 6 \pmod{7}\)

Notice that in each case, the remainder is one less than the divisor. This means that \(x+1\) will be divisible by 5, 6, and 7. Therefore, \(x+1\) is a common multiple of 5, 6, and 7.

To find the least common multiple (LCM) of 5, 6, and 7, we find the prime factorization of each number:

  • 5 = 5
  • 6 = 2 × 3
  • 7 = 7

The LCM is the product of the highest powers of all prime factors present in the numbers: \(LCM(5, 6, 7) = 2 × 3 × 5 × 7 = 210\).

So, \(x + 1 = 210\). Solving for \(x\), we get \(x = 210 - 1 = 209\).

Therefore, the least number which when divided by 5, 6, and 7 leaves remainders 4, 5, and 6 is 209.

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Similar Questions

  1. The HCF of the numbers 310, 208, and 180 is:

  2. If LCM(27, n) = 54, and HCF(27, n) = 9, then the value of n is:

  3. The highest common factor of a set of coprime numbers is equal to:

  4. Two numbers are in ratio 3 : 2. Their LCM and HCF are 24 and 4, respectively. Find the greater number.

  5. The LCM of two numbers is 84. If the numbers are in the ratio 2 : 3, then the sum of the numbers is:

  6. What is the least positive number that can be added to 2488 so that it is completely divisible by 3, 4, 5, and 6?

  7. Find the HCF of 24, 36 and 102.
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  9. What is the difference between the HCF and LCM of 184 and 345?
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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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