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Question

The HCF and LCM of two numbers are in the ratio of 1: 30 and the difference between the HCF and LCM is 493. Find the product of LCM and HCF.

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
8670

The problem involves finding the product of the Highest Common Factor (HCF) and the Lowest Common Multiple (LCM) of two numbers, given their ratio and the difference between them.

Solving HCF LCM Ratio and Difference

Let the HCF of the two numbers be $H$ and the LCM be $L$.

We are given that the ratio of HCF to LCM is 1:30. This can be written as:

$ \frac{H}{L} = \frac{1}{30} $

This implies that $L = 30H$.

We are also given that the difference between the LCM and HCF is 493:

$ L - H = 493 $

Calculating HCF and LCM

Substitute $L = 30H$ into the difference equation:

$ 30H - H = 493 $

$ 29H = 493 $

Now, solve for $H$:

$ H = \frac{493}{29} $

$ H = 17 $

So, the HCF is 17.

Now, calculate the LCM using $L = 30H$:

$ L = 30 \times 17 $

$ L = 510 $

The LCM is 510.

Finding the Product of LCM and HCF

The question asks for the product of the LCM and HCF.

Product = $L \times H$

Product = $510 \times 17$

Product = $8670$

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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?

  2. A and B are two prime numbers such that A > B and their LCM is 209. The value of A 2 - B is:

  3. Find the least number which when divided by 12, 18, 24 and 30 leaves 4 as remainder in each case, but when divided by 7 leaves no remainder.

  4. Calculate the HCF of \(\frac{12}{5}\) \(\frac{14}{15}\)  and  \(\frac{16}{17}\) .

  5. Three numbers are in the proportion of 3 : 8 : 15 and their LCM is 8280. What is their HCF?

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