Calculate 10% of 2kg: Finding Chocolate Content in Cake

Q: Why do I divide the percentage by 100?

Because percent means 'per hundred'! When we write 10%, it means 10 out of 100, which equals $ \frac{10}{100} = 0.1 $ as a decimal.

Q: Can I solve this without converting to decimal?

Yes! You can use the fraction form: $ \frac{10}{100} \times 2 = \frac{20}{100} = 0.2 $. Both methods give the same answer.

Q: How do I check if 0.2kg makes sense?

Think logically: 10% is a small portion, so the answer should be much less than 2kg. Since 0.2kg is indeed much smaller than 2kg, our answer makes sense!

Q: What if the percentage was 50% instead?

For 50%, you'd calculate $ 0.5 \times 2 = 1 $kg. Notice that 50% gives you half the total amount, which is a good way to double-check your work!

Q: Do I need to include units in my final answer?

Always include units! The question asks for kg of chocolate, so your answer should be 0.2kg, not just 0.2. Units make your answer complete and meaningful.

Percentage Calculations with Real-World Applications

The weight of a cake is 2 kg, 10% of which is chocolate.

How many kg of chocolate are there in the cake?

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Step-by-step written solution

Follow each step carefully to understand the complete solution

Understand the problem

The weight of a cake is 2 kg, 10% of which is chocolate.

How many kg of chocolate are there in the cake?

Step-by-step solution

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

Step 1: Identify the given information
Step 2: Apply the appropriate formula
Step 3: Perform the necessary calculations

Now, let's work through each step:

Step 1: The total weight of the cake is $2\, \text{kg}$ , and chocolate makes up $10\%$ of this.

Step 2: To find the weight of the chocolate, we use the formula: $\text{Chocolate weight} = \left( \frac{\text{Percentage}}{100} \right) \times \text{Total weight of the cake}$ This is: $\text{Chocolate weight} = \left( \frac{10}{100} \right) \times 2$

Step 3: Performing the calculation: $= 0.1 \times 2 = 0.2$

Therefore, the weight of the chocolate in the cake is $0.2\, \text{kg}$ .

Checking the multiple-choice options, the correct choice is the one with $0.2$ , which corresponds to choice $4$ .

Final Answer

0.2

Key Points to Remember

Essential concepts to master this topic

Formula: Percentage of amount = (percentage ÷ 100) × total amount
Technique: Convert 10% to 0.1, then multiply: 0.1 × 2kg = 0.2kg
Check: Verify 0.2kg is 1/10 of 2kg since 10% = 1/10 ✓

Common Mistakes

Avoid these frequent errors

Forgetting to divide percentage by 100
Don't multiply 10 × 2 = 20kg! This treats 10% as 10, giving a massively wrong answer. The percentage must be converted to decimal form first. Always divide the percentage by 100 before multiplying.

Practice Quiz

Test your knowledge with interactive questions

Calculate 30 over 100 as a percentage:

FAQ

Everything you need to know about this question

Why do I divide the percentage by 100?

Because percent means 'per hundred'! When we write 10%, it means 10 out of 100, which equals $\frac{10}{100} = 0.1$ as a decimal.

Can I solve this without converting to decimal?

Yes! You can use the fraction form: $\frac{10}{100} \times 2 = \frac{20}{100} = 0.2$ . Both methods give the same answer.

How do I check if 0.2kg makes sense?

Think logically: 10% is a small portion, so the answer should be much less than 2kg. Since 0.2kg is indeed much smaller than 2kg, our answer makes sense!

What if the percentage was 50% instead?

For 50%, you'd calculate $0.5 \times 2 = 1$ kg. Notice that 50% gives you half the total amount, which is a good way to double-check your work!

Do I need to include units in my final answer?

Always include units! The question asks for kg of chocolate, so your answer should be 0.2kg, not just 0.2. Units make your answer complete and meaningful.

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