How to Calculate 7% of 40: A Step-by-Step Solution

Q: Why do I divide by 100 when calculating percentages?

The word percent literally means 'per hundred'! So 7% means 7 out of every 100. To convert to decimal form, you must divide by 100: 7 ÷ 100 = 0.07.

Q: Can I calculate this a different way?

Yes! You can also think of it as: $ \frac{7}{100} \times 40 $. This gives the same result: $ \frac{7 \times 40}{100} = \frac{280}{100} = 2.8 $.

Q: How can I check if 2.8 is really 7% of 40?

Work backwards! Divide your answer by the original number: $ \frac{2.8}{40} = 0.07 $. Then convert to percentage: 0.07 × 100 = 7% ✓

Q: Is there a shortcut for percentage problems?

Yes! Remember that 1% of any number is just that number ÷ 100. So 1% of 40 = 0.4, and 7% of 40 = 7 × 0.4 = 2.8.

Step-by-step video solution

Watch the teacher solve the problem with clear explanations

00:00 Calculate 7 percent of 40

00:07 In order to calculate a certain percentage, convert from percentages to fractions

00:18 For example, 7 percent is 7 divided by 100

00:28 Apply this formula to our exercise, and multiply 7 percent by 40

00:35 Place the multiplication in the numerator

00:44 Break down 40 into factors of 2 and 20

00:48 Break down 100 into factors of 20 and 5

00:51 Reduce wherever possible

01:03 This is the solution

Step-by-step written solution

Follow each step carefully to understand the complete solution

1

Understand the problem

Calculate 7% of 40:

2

Step-by-step solution

To solve this problem, we will follow a simple process using the percentage formula.

Step 1: Identify the percentage and the quantity. Here, the percentage is 7%, and the quantity is 40.
Step 2: Apply the percentage formula: $\text{Percentage Value} = \frac{7}{100} \times 40$ .
Step 3: Calculate the result. First, compute the multiplication: $7 \times 40 = 280$ . Following that, divide by 100: $\frac{280}{100} = 2.8$ .

Therefore, the solution to the problem is $2.8$ .

3

Final Answer

2.8

Key Points to Remember

Essential concepts to master this topic

Formula: Percentage = (Percent ÷ 100) × Number
Technique: Convert 7% to 0.07, then multiply: 0.07 × 40
Check: Verify 2.8 is 7% of 40 by dividing: 2.8 ÷ 40 = 0.07 ✓

Common Mistakes

Avoid these frequent errors

Multiplying by the percentage directly without converting
Don't multiply 7 × 40 = 280 as your final answer! This gives the wrong result because you forgot to convert the percentage. Always divide by 100 first: 7% means 7 ÷ 100 = 0.07.

Practice Quiz

Test your knowledge with interactive questions

Calculate 15% of 100:

FAQ

Everything you need to know about this question

Why do I divide by 100 when calculating percentages?

+

The word percent literally means 'per hundred'! So 7% means 7 out of every 100. To convert to decimal form, you must divide by 100: 7 ÷ 100 = 0.07.

Can I calculate this a different way?

+

Yes! You can also think of it as: $\frac{7}{100} \times 40$ . This gives the same result: $\frac{7 \times 40}{100} = \frac{280}{100} = 2.8$ .

What if I get a different decimal answer?

+

Double-check your calculation! Make sure you're dividing by 100, not multiplying by 100. Also verify your multiplication: 7 × 40 = 280, then 280 ÷ 100 = 2.8.

How can I check if 2.8 is really 7% of 40?

+

Work backwards! Divide your answer by the original number: $\frac{2.8}{40} = 0.07$ . Then convert to percentage: 0.07 × 100 = 7% ✓

Is there a shortcut for percentage problems?

+

Yes! Remember that 1% of any number is just that number ÷ 100. So 1% of 40 = 0.4, and 7% of 40 = 7 × 0.4 = 2.8.

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