Calculate 70% of 90: Step-by-Step Solution

Q: Why do I need to convert 70% to a fraction first?

Percentages are parts of 100, so 70% means 70 out of 100. Converting to $\frac{7}{10}$ makes the multiplication much easier than working with decimals!

Q: Can I just multiply 90 × 0.7 instead?

Absolutely! Converting 70% to the decimal 0.7 works perfectly: 90 × 0.7 = 63. Use whichever method feels more comfortable to you.

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

Divide your answer by the original number: 63 ÷ 90 = 0.7 = 70%. If you get back the original percentage, your answer is correct!

Q: Is there a faster way to calculate this in my head?

Yes! Since 70% = 7/10, think: "What's 7/10 of 90?" 90 ÷ 10 = 9, then 9 × 7 = 63. Breaking it into steps makes mental math easier!

Step-by-step video solution

Watch the teacher solve the problem with clear explanations

00:03 Let's calculate seventy percent of ninety.

00:07 First, change seventy percent into a fraction.

00:12 So, seventy percent becomes seventy over one hundred.

00:17 Now, multiply this fraction by ninety.

00:29 Break it down into factors, and simplify if you can.

00:37 And there you have it. That's the solution!

Step-by-step written solution

Follow each step carefully to understand the complete solution

1

Understand the problem

Calculate 70% of 90:

2

Step-by-step solution

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

Step 1: Convert the percentage to a fraction.
Step 2: Multiply the fraction by the whole number.
Step 3: Simplify the result to find the final answer.

Now, let's work through each step:

Step 1: Convert 70% to a fraction. 70% is equal to $\frac{70}{100}$ , which simplifies further to $\frac{7}{10}$ .

Step 2: Multiply the fraction by the whole number 90. We calculate:

$\frac{7}{10} \times 90 = \frac{7 \times 90}{10} = \frac{630}{10}$ .

Step 3: Simplify $\frac{630}{10}$ :

The numerator 630 divided by the denominator 10 gives us 63.

Therefore, the solution to the problem is 63.

3

Final Answer

63

Key Points to Remember

Essential concepts to master this topic

Rule: Convert percentage to fraction first, then multiply
Technique: 70% = 7/10, so 7/10 × 90 = 630/10
Check: 63 is 70% of 90 because 63 ÷ 90 = 0.7 ✓

Common Mistakes

Avoid these frequent errors

Multiplying by the percentage directly without converting
Don't multiply 90 × 70 = 6300! This treats 70% as 70 instead of 0.7, giving a result 100 times too large. Always convert the percentage to a decimal (70% = 0.7) or fraction (70% = 7/10) first.

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 need to convert 70% to a fraction first?

+

Percentages are parts of 100, so 70% means 70 out of 100. Converting to $\frac{7}{10}$ makes the multiplication much easier than working with decimals!

Can I just multiply 90 × 0.7 instead?

+

Absolutely! Converting 70% to the decimal 0.7 works perfectly: 90 × 0.7 = 63. Use whichever method feels more comfortable to you.

What if I get a different percentage like 25% or 85%?

+

The same process works for any percentage! Convert to a fraction: 25% = 1/4, 85% = 17/20, then multiply by your number.

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

+

Divide your answer by the original number: 63 ÷ 90 = 0.7 = 70%. If you get back the original percentage, your answer is correct!

Is there a faster way to calculate this in my head?

+

Yes! Since 70% = 7/10, think: "What's 7/10 of 90?" 90 ÷ 10 = 9, then 9 × 7 = 63. Breaking it into steps makes mental math easier!

🌟 Unlock Your Math Potential

Get unlimited access to all 18 Percentage questions, detailed video solutions, and personalized progress tracking.

📹

Unlimited Video Solutions

Step-by-step explanations for every problem

📊

Progress Analytics

Track your mastery across all topics

🚫

Ad-Free Learning

Focus on math without distractions

No credit card required • Cancel anytime

Calculate 70% of 90: Step-by-Step Solution

Percentage Calculations with Fraction Conversion

❤️ Continue Your Math Journey!