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Question

The L.C.M. of two numbers is 210 and their H.C.F. is 3. If the first number is divided by 3, the quotient is 7 and the remainder is 0. The second number is:

This question was previously asked in
RRB NTPC 2025 Under Graduate CBT 1 Question Paper PDF (20-Jun-2026) (Shift 3)
The correct answer is

30

Given that the first number divided by 3 gives quotient 7 with remainder 0, the first number is \(3\times 7 = 21\).

For any two numbers, product = LCM × HCF, i.e. \(a\times b = \text{LCM}\times\text{HCF}\).

Substitute: \(21\times b = 210\times 3 = 630\).

Solve: \(b = \dfrac{630}{21} = 30\).

Hence, the second number is 30.

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Important Questions from LCM and HCF

  1. Six bells begin to toll together and toll, respectively, at intervals of 3, 4, 6, 7, 8 and 12 seconds. After how many seconds, will they toll together again?

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