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Question

Alloy X contains 70% copper and 30% zinc. Alloy Y contains 40% copper, 25% zinc and 35% aluminium. Alloy X and Y are mixed in the ratio of 1 ∶ 3. What is the ratio of copper and zinc in the newly formed alloy? 

The correct answer is

38 ∶ 21

Understanding the Alloy Mixing Problem

This problem requires us to determine the final ratio of copper and zinc in a new alloy formed by mixing two different alloys, Alloy X and Alloy Y, in a specific proportion. The initial composition of each alloy is given as percentages of its constituent metals.

Composition of the Starting Alloys

Let's first understand the metallic content of the alloys we are mixing.

Alloy X Composition

Alloy X is composed of:

  • Copper: \(70\%\)
  • Zinc: \(30\%\)

Alloy Y Composition

Alloy Y contains three metals:

  • Copper: \(40\%\)
  • Zinc: \(25\%\)
  • Aluminium: \(35\%\)

Mixing Alloys X and Y

Alloy X and Alloy Y are mixed in the ratio of \(1:3\). To make calculations simple, let's assume we take 1 unit weight of Alloy X and 3 unit weights of Alloy Y. The total weight of the resulting new alloy will be \(1 + 3 = 4\) units.

Calculating Component Amounts in the New Alloy

Now, we calculate the actual amount (in units of weight) of copper and zinc contributed by each alloy based on the mixing ratio.

From 1 unit of Alloy X:

  • Amount of Copper from X = \(70\%\) of 1 = \(0.70 \times 1 = 0.70\) units
  • Amount of Zinc from X = \(30\%\) of 1 = \(0.30 \times 1 = 0.30\) units

From 3 units of Alloy Y:

  • Amount of Copper from Y = \(40\%\) of 3 = \(0.40 \times 3 = 1.20\) units
  • Amount of Zinc from Y = \(25\%\) of 3 = \(0.25 \times 3 = 0.75\) units
  • Amount of Aluminium from Y = \(35\%\) of 3 = \(0.35 \times 3 = 1.05\) units

The total amount of each metal in the new alloy is the sum of the amounts contributed by Alloy X and Alloy Y.

Copper Content in the Mixture

Total Copper in the new alloy = Copper from X + Copper from Y

Total Copper = \(0.70\) units + \(1.20\) units = \(1.90\) units

Zinc Content in the Mixture

Total Zinc in the new alloy = Zinc from X + Zinc from Y

Total Zinc = \(0.30\) units + \(0.75\) units = \(1.05\) units

Aluminium Content in the Mixture

Total Aluminium in the new alloy = Aluminium from X + Aluminium from Y

Total Aluminium = \(0\) units + \(1.05\) units = \(1.05\) units (Though not required for the final ratio, it's part of the composition).

Component Amount from Alloy X (1 unit) Amount from Alloy Y (3 units) Total Amount in New Alloy (4 units)
Copper \(0.70\) units \(1.20\) units \(1.90\) units
Zinc \(0.30\) units \(0.75\) units \(1.05\) units
Aluminium \(0\) units \(1.05\) units \(1.05\) units

Determining the Copper to Zinc Ratio

The question asks for the ratio of copper to zinc in the newly formed alloy. This is calculated by taking the total amount of copper and the total amount of zinc in the mixture.

Ratio of Copper : Zinc = Total Copper : Total Zinc

Ratio = \(1.90 : 1.05\)

Simplifying the Final Ratio

To express the ratio \(1.90 : 1.05\) in the simplest form, we can first eliminate the decimals by multiplying both numbers by 100.

Ratio = \(190 : 105\)

Now, we find the greatest common divisor (GCD) of 190 and 105 to simplify the ratio. Both numbers are divisible by 5.

  • \(190 \div 5 = 38\)
  • \(105 \div 5 = 21\)

The simplified ratio of copper to zinc in the newly formed alloy is \(38 : 21\).

Revision Table: Key Concepts in Alloy Mixing Calculations

Concept Description How it Applies Here
Percentage Composition Shows the proportion of each element in an alloy by weight. Used to find the amount of copper, zinc, and aluminium in given quantities of Alloy X and Alloy Y.
Mixing Ratio Indicates the relative amounts (by weight or volume) of components being mixed. The \(1:3\) ratio of Alloy X to Alloy Y determined the base quantities used for calculation (1 unit of X, 3 units of Y).
Total Amount of a Component The sum of the amounts of that component contributed by all parts of the mixture. Total copper is the sum of copper from Alloy X and Alloy Y. Total zinc is the sum of zinc from Alloy X and Alloy Y.
Ratio Simplification Expressing a ratio in its simplest form by dividing both parts by their greatest common divisor. The ratio \(1.90 : 1.05\) was simplified to \(38 : 21\).

Additional Information: Understanding Metal Alloys

An alloy is a mixture of metals or a mixture of a metal and another element. Alloying is done to enhance the properties of pure metals, such as strength, hardness, durability, or corrosion resistance. Common examples include:

  • Brass: A common alloy of copper and zinc, known for its workability and appearance. The varying ratios of copper and zinc result in different types of brass.
  • Bronze: Traditionally an alloy of copper and tin, stronger and more durable than brass.
  • Steel: Primarily an alloy of iron and carbon, with varying amounts of other elements like manganese, chromium, vanadium, and tungsten.
  • Pewter: Historically composed of tin, with the addition of lead, antimony, and copper. Modern pewter is lead-free.

Calculations involving mixing alloys, like the one demonstrated, are fundamental in metallurgy and manufacturing to control the final properties of the material.

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Important Questions from Percentage

  1. Radha saves 25% of her income. If her expenditure increases by 20% and her income increases by 29%, then her savings increase by;

  2. The income of A is 45% more than the income of B and the income of C is 60% less than the sum of the incomes of A and B. The income of D is 20% more than that of C. If the difference between the incomes of B and D is Rs. 13200, then the income (in Rs.) of C is:

  3. The price of cooking oil increased by 25%. Find by how much percentage a family must reduce its consumption in order to maintain the same budget.

  4. The population of a city increased by 30% in the first year and decreased by 15% in the next year. If the present population is 11,050 then population 2 years ago was:

  5. The income of A is 30% less than the income of B and the income of B is 137.5% more than that of C. If the income of A is Rs. 28500 less than that of B, then the income (in Rs.) of C is:

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