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Question

The ratio of two numbers is 3 : 4 and their L.C.M is 180. What is the larger of the two numbers?

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
60

Solving Ratio and LCM Problems

Let the two numbers be represented based on their given ratio. Since the ratio is 3 : 4, we can denote the numbers as $3x$ and $4x$, where $x$ is a common multiplier.

Calculating the LCM

The Least Common Multiple (L.C.M.) of the two numbers, $3x$ and $4x$, can be calculated. Since 3 and 4 have no common factors other than 1 (they are coprime), their L.C.M. is:

L.C.M.($3x$, $4x$) = L.C.M.(3, 4) $\times$ $x$ = $12x$

Finding the Multiplier 'x'

We are given that the L.C.M. of the two numbers is 180. Therefore, we can set up the equation:

$12x = 180$

To find the value of $x$, divide 180 by 12:

$x = \frac{180}{12}$

$x = 15$

Determining the Numbers

Now, substitute the value of $x$ back into the expressions for the two numbers:

  • First number = $3x = 3 \times 15 = 45$
  • Second number = $4x = 4 \times 15 = 60$

Identifying the Larger Number

Compare the two numbers calculated:

  • The numbers are 45 and 60.
  • The larger of the two numbers is 60.
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Similar Questions

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  2. If $a : b :: 3 : 4$ then the value of the expression $\frac{5a - 3b}{7a + 2b}$ is:
  3. If the third proportional of 8 and 20 be x, then what is the value of x?
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Important Questions from Ratio and Proportion

  1. In a mixture of 156 litres, the ratio of milk and water is 7 : 6. How much water should be added to make the ratio 14 : 13?

  2. If the ratio of the first to second number is 3 : 4 and that of the second to the third number is 8 : 5, and sum of three numbers is 190 then the third number is:

  3. The third proportional to 9 and 15 is:

  4. The average age of 3 persons is 30 years.If their ages are in the ratio of 3 : 5 : 7 respectively, then the age of the eldest person is:

  5. The income of A and B are in the ratio 5 : 3. The expenses of A, B and C are in the ratio of 8 : 5 : 2. If C spends 2000 and B saves ₹ 700, then A saves:

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