Calculate Lucy's Monthly Savings: 25% of $5000

Q: Why do I subtract 75% from 100% first?

Because Lucy spends 75%, but the question asks how much she saves. These are opposite amounts that must add up to 100% of her salary!

Q: Can I just calculate 75% of $5000 and subtract from $5000?

Yes! That's another valid method: $ \$5000 - (0.75 \times \$5000) = \$5000 - \$3750 = \$1250 $. Both approaches give the same answer.

Q: How do I convert 25% to a decimal quickly?

Move the decimal point two places left! So 25% becomes 0.25. This works because percent means "per hundred" or divided by 100.

Q: Is there a faster way to calculate 25% of any number?

Yes! Since 25% = 1/4, you can divide by 4 instead: $ \$5000 \div 4 = \$1250 $. This mental math trick works great for 25%, 50%, and 75%!

Percentage Calculations with Complement Operations

The salary Lucy receives each month is 5000 dollars. She spends 75% of the money and saves the rest. How much money does Lucy save per month?

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations

00:00 Determine the amount of money Lucy saves per month

00:05 The percentage of expenses according to the data

00:22 Subtract this percentage from the whole in order to determine the percentage of savings

00:34 This is the monthly savings percentage

00:46 Convert from a percentage to a fraction

00:51 Use the formula to convert percentages to fractions

00:56 Apply this formula to our exercise

01:06 Multiply this fraction by the whole in order to determine Lucy's savings

01:26 Break down 5000 into factors of 100 and 50

01:36 Reduce wherever possible

01:41 This is the solution

Step-by-step written solution

Follow each step carefully to understand the complete solution

Understand the problem

The salary Lucy receives each month is 5000 dollars. She spends 75% of the money and saves the rest. How much money does Lucy save per month?

Step-by-step solution

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

Step 1: Identify the percentage of salary that is saved.
Step 2: Calculate the amount saved using this percentage.

Let's start with Step 1:
Lucy spends 75% of her salary, so she saves $100\% - 75\% = 25\%$ .

Now, Step 2:
We need to determine 25% of her monthly salary of $5000. We use the formula for finding a percentage of a number:

$\text{Amount saved} = \frac{25}{100} \times 5000$

Calculate the multiplication:

$\text{Amount saved} = 0.25 \times 5000 = 1250$

Therefore, Lucy saves $\text{\$1250}$ per month.

Final Answer

1250

Key Points to Remember

Essential concepts to master this topic

Complement Rule: If spending 75%, then saving equals 100% - 75% = 25%
Technique: Convert 25% to decimal: 25/100 = 0.25, then multiply by $5000
Check: Verify $1250 + $3750 = $5000 total salary ✓

Common Mistakes

Avoid these frequent errors

Calculating 75% instead of 25%
Don't calculate 75% of $5000 = $3750 for savings amount! This gives you the spending amount, not savings. Always find the complement percentage first: 100% - 75% = 25%, then calculate 25% of $5000 = $1250.

Practice Quiz

Test your knowledge with interactive questions

Convert the fraction into a percentage:

$\frac{24}{100}=\text{?}$

FAQ

Everything you need to know about this question

Why do I subtract 75% from 100% first?

Because Lucy spends 75%, but the question asks how much she saves. These are opposite amounts that must add up to 100% of her salary!

Can I just calculate 75% of $5000 and subtract from $5000?

Yes! That's another valid method: $\$5000 - (0.75 \times \$5000) = \$5000 - \$3750 = \$1250$ . Both approaches give the same answer.

How do I convert 25% to a decimal quickly?

Move the decimal point two places left! So 25% becomes 0.25. This works because percent means "per hundred" or divided by 100.

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

Always check that spending percentage + saving percentage = 100%. If they don't, re-read the problem carefully - you might have missed some information!

Is there a faster way to calculate 25% of any number?

Yes! Since 25% = 1/4, you can divide by 4 instead: $\$5000 \div 4 = \$1250$ . This mental math trick works great for 25%, 50%, and 75%!

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