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Question

If $a : b = 7 : 9$ and $b : c = 1 : 12$, then $a : b : c$ is:

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
$7 : 9 : 108$

Finding the Combined Ratio $a : b : c$

We are given two ratios:

  • $a : b = 7 : 9$
  • $b : c = 1 : 12$

Our goal is to find the combined ratio $a : b : c$. To do this, the value representing 'b' must be the same in both ratios.

Calculating the Combined Ratio

  1. Identify 'b' values: In the first ratio, $b$ corresponds to 9. In the second ratio, $b$ corresponds to 1.
  2. Equalize 'b': We need to make the 'b' value the same. The least common multiple of 9 and 1 is 9. The first ratio already has $b=9$. We need to adjust the second ratio ($b : c = 1 : 12$) so that $b$ becomes 9.
  3. Adjust the second ratio: Multiply both parts of the second ratio by 9: $b : c = (1 \times 9) : (12 \times 9)$ $b : c = 9 : 108$
  4. Combine the ratios: Now we have: $a : b = 7 : 9$ $b : c = 9 : 108$ Since the 'b' value is 9 in both, we can combine them directly.

Therefore, the combined ratio is $a : b : c = 7 : 9 : 108$.

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Similar Questions

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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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