Download - Splash Screen. Main Idea/Vocabulary proportional proportion cross product Solve proportions
Identify Proportional Relationships
MATH Before dinner, Mohammed solved 8 math problems in 12 minutes. After dinner, he solved 2 problems in 3 minutes. Is the number of problems he solved proportional to the time?
Method 1 Compare unit rates (We did this before).
Since the unit rates are equal, the number of math equations is proportional to the time in minutes.
Identify Proportional Relationships
Method 2 Compare ratios by comparing cross products.
Answer: Since the cross products are equal, the number of math equations is proportional to the time in minutes.
24 = 24Multiply.
?
8 × 3 = 12 × 2 Find the cross products.?
1. A
2. B
A. yes
B. no
Determine if the quantities $30 for 12 gallons of gasoline and $10 for 4 gallons of gasoline are proportional.
Solve a Proportion
5x = 8 ● 18Find the cross
products.
5x = 144Multiply.
Answer: x = 28.8
Write the proportion.
Divide each side by 5.
x= 28.8
Solve a Proportion
3.5 ● n = 14 ● 6Find the cross
products.
3.5n = 84Multiply.
Answer: The solution is 24.
Write the proportion.
Divide each side by 3.5.
n = 24Simplify.
FLAGS According to specifications, the ratio of the length of the U.S. flag to its width must be 1.9 to 1. How long must a U.S. flag be if it is designed to have a width of 2.5 feet?
Answer: The length of a U.S. flag having a width of 2.5 feet must be 4.75 feet.
length Write a proportion.width
Find the cross products.
Multiply.
1. A
2. B
3. C
4. D
A. 72 girls
B. 108 girls
C. 120 girls
D. 148 girls
SCHOOL The ratio of boys to girls at Blue Hills Middle School is 4 to 5. How many girls attend the school if there are 96 boys?