Calculate 70% of 90: Step-by-Step Percentage Problem

Q: Why do I divide by 100 to convert a percentage?

Because percent means "per hundred"! So 70% literally means $ \frac{70}{100} $ or 0.70. This conversion is essential for multiplication.

Q: Can I solve this problem without decimals?

Yes! You can use fractions: $ \frac{70}{100} \times 90 = \frac{70 \times 90}{100} = \frac{6300}{100} = 63 $. Both methods give the same answer!

Q: How do I check if 63 is really 70% of 90?

Divide your answer by the original number: $ \frac{63}{90} = 0.70 $. Convert back to percentage: 0.70 × 100 = 70%. Perfect match!

Q: Is there a shortcut for calculating percentages?

Yes! For easy percentages: 10% = divide by 10, 50% = divide by 2. For 70%, you can find 10% first (9) and multiply by 7: 9 × 7 = 63!

Percentage Calculations with Decimal Conversion

What is 70% of 90?

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations

00:00 Find the part of the whole: Calculate 70% of 90?

00:04 Apply the formula to convert percentages to fractions

00:10 The fraction has a numerator equal to the percentage number and a denominator of 100

00:14 Apply this formula to our exercise

00:21 Multiply the fraction by our whole number

00:26 Break down 70 into factors of 7 and 10, and 100 into factors of 10 and 10

00:41 Break down 90 into factors of 9 and 10

00:46 Reduce wherever possible

00:54 This is the solution

Step-by-step written solution

Follow each step carefully to understand the complete solution

Understand the problem

What is 70% of 90?

Step-by-step solution

To solve the problem of finding 70% of 90, we will use the percentage calculation method:

Step 1: Convert the percentage to a decimal. 70% is equivalent to $\frac{70}{100} = 0.70$ .
Step 2: Multiply the base number, 90, by the decimal equivalent of the percentage.

Let's perform the calculation:

$0.70 \times 90 = 63$

Therefore, 70% of 90 is $\mathbf{63}$ .

Final Answer

Key Points to Remember

Essential concepts to master this topic

Rule: Convert percentage to decimal by dividing by 100
Technique: 70% becomes 0.70, then multiply: 0.70 × 90 = 63
Check: Does 63 ÷ 90 = 0.70 or 70%? Yes ✓

Common Mistakes

Avoid these frequent errors

Forgetting to convert percentage to decimal
Don't multiply 70 × 90 = 6300 thinking that's 70% of 90! This gives a massive wrong answer because you skipped converting the percentage. Always convert the percentage to decimal first by dividing by 100.

Practice Quiz

Test your knowledge with interactive questions

Convert the fraction into a percentage:

$\frac{2}{100}=\text{?}$

FAQ

Everything you need to know about this question

Why do I divide by 100 to convert a percentage?

Because percent means "per hundred"! So 70% literally means $\frac{70}{100}$ or 0.70. This conversion is essential for multiplication.

Can I solve this problem without decimals?

Yes! You can use fractions: $\frac{70}{100} \times 90 = \frac{70 \times 90}{100} = \frac{6300}{100} = 63$ . Both methods give the same answer!

How do I check if 63 is really 70% of 90?

Divide your answer by the original number: $\frac{63}{90} = 0.70$ . Convert back to percentage: 0.70 × 100 = 70%. Perfect match!

What if I get a decimal answer instead of a whole number?

That's completely normal! Many percentage problems result in decimal answers. Just make sure to round appropriately if the problem asks for it.

Is there a shortcut for calculating percentages?

Yes! For easy percentages: 10% = divide by 10, 50% = divide by 2. For 70%, you can find 10% first (9) and multiply by 7: 9 × 7 = 63!

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