# Lesson 15: Finding This Percent of That

Let’s solve percentage problems like a pro.

## 15.1: Number Talk: Decimals

Find the value of each expression mentally.

$(0.23) \boldcdot 100$

$50 \div 100$

$145 \boldcdot \frac{1}{100}$

$7 \div 100$

## 15.2: Audience Size

A school held several evening activities last month—a music concert, a basketball game, a drama play, and literacy night. The music concert was attended by 250 people. How many people came to each of the other activities?

1. Attendance at a basketball game was 30% of attendance at the concert.
2. Attendance at the drama play was 140% of attendance at the concert.
1. Attendance at literacy night was 44% of attendance at the concert.

## 15.3: Everything is On Sale

During a sale, every item in a store is 80% of its regular price.

1. If the regular price of a T-shirt is \$10, what is its sale price? 2. The regular prices of five items are shown here. Find the sale price of each item. item 1 item 2 item 3 item 4 item 5 row 1 regular price \$1 \$4 \$10 \$55 \$120
row 2 sale price
3. You found 80% of many values. Was there a process you repeated over and over to find the sale prices? If so, describe it.

4. Which of the following expressions could be used to find 80% of $x$? Be prepared to explain your reasoning.

$\frac{8}{100} \boldcdot x$

$\frac{80}{100} \boldcdot x$

$\frac{8}{10} \boldcdot x$

$\frac{4}{10} \boldcdot x$

$\frac85 \boldcdot x$

$\frac45 \boldcdot x$

$80 \boldcdot x$

$8 \boldcdot x$

$(0.8) \boldcdot x$

$(0.08) \boldcdot x$

## Summary

To find 49% of a number, we can multiply the number by $\frac{49}{100}$ or 0.49.

To find 135% of a number, we can multiply the number by $\frac{135}{100}$ or 1.35.

To find 6% of a number, we can multiply the number by $\frac{6}{100}$ or 0.06.

In general, to find $P\%$ of $x$, we can multiply: $$\frac{P}{100} \boldcdot x$$