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Question

A mixture of fog contains water and air in the ratio 5 ∶ 3. On adding 8 liters of air, the ratio of water and air becomes 1 ∶ 1. The quantity of water in the original fog is: 

The correct answer is

20 litres

Understanding the Initial Fog Mixture

The problem describes a fog mixture containing water and air. The initial ratio of water to air is given as 5 ∶ 3. This means that for every 5 parts of water, there are 3 parts of air.

Let the initial quantity of water be $5x$ liters and the initial quantity of air be $3x$ liters, where $x$ is a common multiplier.

Calculating Changes in the Mixture

Next, 8 liters of air are added to this mixture. The quantity of water remains unchanged, but the quantity of air increases.

  • Initial quantity of water = $5x$ liters
  • Initial quantity of air = $3x$ liters
  • Quantity of air added = 8 liters
  • New quantity of air = $(3x + 8)$ liters
  • Quantity of water after adding air = $5x$ liters

Determining the New Ratio

After adding the air, the ratio of water to air becomes 1 ∶ 1. This implies that the quantities of water and air are now equal in the mixture.

We can set up an equation based on this new ratio:

$$ \frac{\text{Quantity of Water}}{\text{New Quantity of Air}} = \frac{1}{1} $$

Substituting the expressions for water and air quantities:

$$ \frac{5x}{3x + 8} = \frac{1}{1} $$

Solving for the Unknown Multiplier

To find the value of $x$, we can cross-multiply the equation:

$$ 5x \times 1 = 1 \times (3x + 8) $$

$$ 5x = 3x + 8 $$

Now, we need to isolate $x$. Subtract $3x$ from both sides of the equation:

$$ 5x - 3x = 8 $$

$$ 2x = 8 $$

Divide both sides by 2 to find the value of $x$:

$$ x = \frac{8}{2} $$

$$ x = 4 $$

Finding the Original Quantity of Water

The question asks for the quantity of water in the original fog. We established that the original quantity of water is $5x$ liters.

Substitute the value of $x = 4$ into the expression for the original quantity of water:

Original quantity of water = $5 \times x$

Original quantity of water = $5 \times 4$

Original quantity of water = $20$ liters

Verification

Let's check if this result satisfies the conditions:

  • Original water = 20 liters
  • Original air = $3x = 3 \times 4 = 12$ liters
  • Initial ratio = 20:12 = 5:3 (Correct)
  • Add 8 liters of air: New air = $12 + 8 = 20$ liters
  • New ratio = Water:Air = 20:20 = 1:1 (Correct)

Therefore, the original quantity of water in the fog was 20 liters.

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Important Questions from To Make a Mixture from Two Mixtures

  1. In a 90 litre solution, acid and water are in the ratio 2 ∶ 1, To make the ratio of acid and water as 1 ∶ 2, how many litre of water should be added to the solution?

  2. In a milk and water solution, the ratio of milk to water is 1 : 4. M litres of milk is added in it and ratio become 1 : 3. Again N litres of water is added in it and ratio become 2 : 7. If N – M = 4, then what is the initial quantity of solution?

  3. A mixture contains acid and alcohol in the ratio of 3 : 2. On adding 10 litres of alcohol in mixture, the ratio of acid to alcohol becomes 3 : 5. The quantity of acid (in litres) in the original mixture was:

  4. How many litres of acid are there in 12 litres of a 20% solution?

  5. The ratio of number of male and female employees in a company was 5 ∶ 4. Some new males and females joined the company in the ratio 2 ∶ 3. The total number of employees become 1620 and the ratio of males to females become 68 ∶ 67. Initially what was the total number of employees in the company?

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