Cross multiplication is a powerful method for solving proportions with... Show more
How to Cross Multiply to Solve Ratio Problems with Examples

Changing Ratios and Algebraic Solutions
This page focuses on solving changing ratio problems with algebra, providing a comprehensive example and step-by-step solution process.
The example problem involves Jan and Kim's marbles, initially in a ratio of 5:6. After Jan gains 2 marbles, the new ratio becomes 7:8. The goal is to determine how many marbles each owned initially.
Example: Jan and Kim own numbers of marbles that are in the ratio 5:6. Jan gains 2 more marbles and the ratio is now 7:8. How many marbles do each own initially?
The solution process involves:
- Writing the initial ratio in algebraic form (5x : 6x)
- Expressing the new ratio after the change
- Setting up an equation based on the new ratio
- Using cross multiplication to solve for x
- Substituting the value of x to find the original numbers of marbles
Highlight: This problem demonstrates how to apply algebraic techniques to solve complex ratio problems involving changes in quantities.
The solution reveals that initially, Jan owned 40 marbles and Kim owned 48 marbles.
Vocabulary: Changing ratios refer to situations where the ratio between quantities changes due to an increase or decrease in one or more of the quantities involved.
This example illustrates the power of algebra in solving ratio problems, especially when dealing with changing ratios. It combines the concepts of cross multiplication, algebraic manipulation, and ratio analysis to arrive at a precise solution.
Quote: "Initially Jan owned 40, Kim owned 48"
This page provides valuable practice for students preparing for exams like GCSE, where changing ratio questions and algebraic ratio GCSE questions are common.

Solving Ratio Problems with Cross Multiplication
This page introduces the concept of using cross multiplication to solve ratio problems with variables. It provides a step-by-step example of how to apply this method effectively.
The example problem involves two brothers, Rich and Andrew, sharing money in a ratio of 2:7, with Andrew receiving £30 more than Rich. The solution demonstrates how to use blocks to represent the ratio and solve for the total amount shared.
Example: Two brothers, Rich and Andrew, share a sum of money in the ratio 2:7. Andrew gets £30 more than Rich. Calculate how much the brothers share.
The solution process involves:
- Representing the difference between the ratio parts (7 - 2 = 5)
- Assigning a value to the difference
- Calculating the value of one block (£6)
- Determining the total amount shared (6 × (7 + 2) = £54)
Highlight: This method of using blocks to represent ratio parts is particularly useful for visualizing and solving ratio problems.
The page also covers finding the value of n in a ratio, using the example : 2n = 3 : 5. This introduces the concept of cross multiplication for solving proportions with variables.
Vocabulary: Cross multiplication is a technique used to solve proportions by multiplying the numerator of each fraction by the denominator of the other fraction.
The solution process for finding n involves:
- Cross multiplying the ratios
- Simplifying the resulting equation
- Solving for n
Definition: The cross multiplication property of proportion states that if a:b = c:d, then ad = bc.
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How to Cross Multiply to Solve Ratio Problems with Examples
Cross multiplication is a powerful method for solving proportions with variables. This guide explores its application in ratio problems and changing ratios.
- Learn how to use cross multiplication to solve ratio problems with variables
- Understand the cross multiplication property... Show more

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Changing Ratios and Algebraic Solutions
This page focuses on solving changing ratio problems with algebra, providing a comprehensive example and step-by-step solution process.
The example problem involves Jan and Kim's marbles, initially in a ratio of 5:6. After Jan gains 2 marbles, the new ratio becomes 7:8. The goal is to determine how many marbles each owned initially.
Example: Jan and Kim own numbers of marbles that are in the ratio 5:6. Jan gains 2 more marbles and the ratio is now 7:8. How many marbles do each own initially?
The solution process involves:
- Writing the initial ratio in algebraic form (5x : 6x)
- Expressing the new ratio after the change
- Setting up an equation based on the new ratio
- Using cross multiplication to solve for x
- Substituting the value of x to find the original numbers of marbles
Highlight: This problem demonstrates how to apply algebraic techniques to solve complex ratio problems involving changes in quantities.
The solution reveals that initially, Jan owned 40 marbles and Kim owned 48 marbles.
Vocabulary: Changing ratios refer to situations where the ratio between quantities changes due to an increase or decrease in one or more of the quantities involved.
This example illustrates the power of algebra in solving ratio problems, especially when dealing with changing ratios. It combines the concepts of cross multiplication, algebraic manipulation, and ratio analysis to arrive at a precise solution.
Quote: "Initially Jan owned 40, Kim owned 48"
This page provides valuable practice for students preparing for exams like GCSE, where changing ratio questions and algebraic ratio GCSE questions are common.

Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Solving Ratio Problems with Cross Multiplication
This page introduces the concept of using cross multiplication to solve ratio problems with variables. It provides a step-by-step example of how to apply this method effectively.
The example problem involves two brothers, Rich and Andrew, sharing money in a ratio of 2:7, with Andrew receiving £30 more than Rich. The solution demonstrates how to use blocks to represent the ratio and solve for the total amount shared.
Example: Two brothers, Rich and Andrew, share a sum of money in the ratio 2:7. Andrew gets £30 more than Rich. Calculate how much the brothers share.
The solution process involves:
- Representing the difference between the ratio parts (7 - 2 = 5)
- Assigning a value to the difference
- Calculating the value of one block (£6)
- Determining the total amount shared (6 × (7 + 2) = £54)
Highlight: This method of using blocks to represent ratio parts is particularly useful for visualizing and solving ratio problems.
The page also covers finding the value of n in a ratio, using the example : 2n = 3 : 5. This introduces the concept of cross multiplication for solving proportions with variables.
Vocabulary: Cross multiplication is a technique used to solve proportions by multiplying the numerator of each fraction by the denominator of the other fraction.
The solution process for finding n involves:
- Cross multiplying the ratios
- Simplifying the resulting equation
- Solving for n
Definition: The cross multiplication property of proportion states that if a:b = c:d, then ad = bc.
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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Most popular content: Ratio
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Explore in-depth analysis and key quotes for characters in J.B. Priestley's 'An Inspector Calls'. This resource covers Gerald Croft, Inspector Goole, Sheila Birling, Mrs. Birling, Eric Birling, and Eva Smith, focusing on themes of class, gender roles, and social responsibility. Ideal for students aiming for Grade 8 and above.
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Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.