RS Aggarwal Solutions Class 7 Chapter-9 Unitary Method (Ex 9B) Exercise 9.2 - Free PDF
FAQs on RS Aggarwal Solutions Class 7 Chapter-9 Unitary Method (Ex 9B) Exercise 9.2
1. How do I use the RS Aggarwal Solutions for Class 7 Maths Chapter 9 to correctly solve problems in Exercise 9.2?
These solutions offer a step-by-step guide for each problem in Exercise 9.2. First, carefully read the question to determine if it involves direct or inverse proportion. The solutions then demonstrate how to calculate the value of a single unit (e.g., the work done by one person in a day) and subsequently multiply or divide to find the final required value, aligning with the method prescribed in the CBSE 2025-26 syllabus.
2. What is the most important first step when solving a word problem from Exercise 9.2 using the unitary method?
The crucial first step is to identify the relationship between the two quantities in the problem. You must figure out if they are in direct proportion, where both values increase or decrease together (like the number of books and their total cost), or in inverse proportion, where one value increases as the other decreases (like the number of workers and the time taken to finish a job). This single decision determines how you will solve the entire problem.
3. How do I know when to apply the concept of inverse proportion for questions in this exercise?
You should use inverse proportion when one quantity increases while the other systematically decreases. Common examples you will find in this chapter include:
- More people finishing a task in less time.
- A vehicle moving at a higher speed taking less time to cover the same distance.
- A food supply for a group of people lasting for fewer days if more people join.
4. Why is calculating the value of 'one unit' a mandatory step in the unitary method?
Finding the value of a single unit is the fundamental principle of this method because it establishes a standard reference point. This baseline allows you to calculate the value for any other required quantity with a simple multiplication or division. For example, by knowing the cost of 'one' apple, you can easily determine the cost of 20 apples. This technique transforms complex ratio problems into a straightforward two-step process: find the value of one, then find the value of many.
5. What is the key difference in the calculation for a direct proportion problem versus an inverse proportion problem?
The key difference lies in the final calculation step after finding the value of one unit.
- In direct proportion, you multiply the value of the single unit by the required number of units. (e.g., cost of 1 pen x 10 = cost of 10 pens).
- In inverse proportion, you divide the value of the single unit by the required number of units. (e.g., time for 1 worker / 10 = time for 10 workers).
6. How can I quickly check if my answer to a problem in Exercise 9.2 is logically correct?
After finding your answer, perform a quick logical check. Ask yourself if the result makes sense in the real world. For instance:
- For a direct proportion problem, if you buy more items, the total cost should be higher.
- For an inverse proportion problem, if more workers are doing a job, the time taken must be less.
