Calculate the Price of a 100g Alloy: Iron-Aluminum Cost Breakdown

Weighted Average Calculations with Cost Components

A durable alloy is made of iron and aluminum.

30% of the alloy is aluminum costing 5per100grams,while705 per 100 grams, while 70% is iron costing 17 per 100 grams.

What is the price of 100 grams of the alloy?

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1

Understand the problem

A durable alloy is made of iron and aluminum.

30% of the alloy is aluminum costing 5per100grams,while705 per 100 grams, while 70% is iron costing 17 per 100 grams.

What is the price of 100 grams of the alloy?

2

Step-by-step solution

To solve this problem, we'll follow these steps:

  • Identify the contribution of the aluminum component to the overall cost.

  • Identify the contribution of the iron component to the overall cost.

  • Combine the contributions to find the total cost of the alloy.

Let's perform the calculations:

1. Aluminum's Contribution:
The alloy is 30% aluminum, which costs 5 per 100 grams. Hence, the contribution from aluminum is:
\( 0.30 \times 5 = 1.5 \text{ dollars}

2. Iron's Contribution:
The alloy is 70% iron, which costs 17 per 100 grams. Hence, the contribution from iron is:
\( 0.70 \times 17 = 11.9 \text{ dollars}

3. Total Cost of the Alloy:
To obtain the total cost of 100 grams of the alloy, we add the contributions from both components:
1.5+11.9=13.4 dollars 1.5 + 11.9 = 13.4 \text{ dollars}

Therefore, the price of 100 grams of the alloy is 13.4 dollars 13.4 \text{ dollars} .

3

Final Answer

13.4 13.4 $

Key Points to Remember

Essential concepts to master this topic
  • Weighted Average Rule: Each component's cost equals its percentage times unit price
  • Technique: Calculate aluminum: 0.30 × 5=5 = 1.50, iron: 0.70 × 17=17 = 11.90
  • Check: Verify percentages add to 100% and final cost seems reasonable ✓

Common Mistakes

Avoid these frequent errors
  • Adding percentages directly to costs
    Don't add 30% + 5+705 + 70% + 17 = wrong units and meaningless result! This mixes percentages with dollar amounts incorrectly. Always multiply each percentage (as decimal) by its corresponding cost first.

Practice Quiz

Test your knowledge with interactive questions

Norbert buys some new clothes.

When he gets home, he decides to work out how much each outfit cost him on average.

PriceOutfit4 T-shirts2 pairs of shorts3 pairs of pants2 sweaters45$50$80$100$210$1 coat

What answer should he come up with?

FAQ

Everything you need to know about this question

Why do I convert percentages to decimals?

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Percentages must become decimals for multiplication! 30% = 0.30 and 70% = 0.70. This lets you properly calculate each component's contribution to the total cost.

What if the percentages don't add up to 100%?

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Check your work immediately! In alloy problems, all components must add to exactly 100%. If they don't, reread the problem carefully for missing information.

Can I just average the two costs instead?

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No! A simple average ignores the different amounts of each material. You need the weighted average because there's more iron (70%) than aluminum (30%).

How do I know my final answer makes sense?

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Your answer should be between the two individual costs. Since iron costs 17andaluminumcosts17 and aluminum costs 5, expect your alloy cost between 55-17, closer to iron's price since there's more iron.

What if I get confused with the decimal multiplication?

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Break it down step by step: 0.30×5=30100×5=150100=1.5 0.30 \times 5 = \frac{30}{100} \times 5 = \frac{150}{100} = 1.5 . Take your time with each calculation!

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