Understanding Proportions and Cross Multiplication

This video tutorial covers the concept of proportions and introduces cross multiplication as a method to solve them. It begins with a basic explanation of proportions, which are two ratios set equal to each other, and explains how cross multiplication can be used to find missing values. The tutorial includes several examples, demonstrating the step-by-step process of solving proportions using cross multiplication and long division. Additionally, it applies these techniques to real-world scenarios, such as calculating the number of entrees sold at a restaurant or determining the number of fiction books in a library.

What is a proportion in mathematics?

• Two equal ratios

• A multiplication problem

• A single fraction

• A division problem

Tags

CCSS.7.RP.A.3

What is the first step in solving a proportion using cross multiplication?

• Add the numerators

• Subtract the fractions

• Multiply the denominators

• Cross multiply the terms

Tags

CCSS.3.OA.A.4

In the example where 5 times 7 equals 2 times X, what is the value of X?

• 14

• 17.5

• 7

• 35

If X over 10 equals 5 over 9, what is the value of X?

• 10

• 9

• 5.5 repeating

• 5.5

Tags

CCSS.6.RP.A.3B

How many entrees would be sold if 20 appetizers are sold, given the ratio of 8 entrees to 3 appetizers?

• 50

• 45

• 60

• 53

In a library, if there are 147 non-fiction books, how many fiction books are there given the ratio of 7 non-fiction to 9 fiction?

• 189

• 147

• 210

• 63

What is the total number of vet technicians if the ratio of vet technicians to veterinarians is 5 to 2 and the total staff is 42?

• 24

• 42

• 30

• 12

Tags

CCSS.6.RP.A.3B

How many minutes will Jason practice after 5 weeks if he practices 25 minutes every 2 days?

• 350

• 525

• 400

• 437.5

Tags

CCSS.6.RP.A.3B