RS Aggarwal Solutions Class 7 Chapter-12 Simple Interest (Ex 12B) Exercise 12.2 - Free PDF
FAQs on RS Aggarwal Solutions Class 7 Chapter-12 Simple Interest (Ex 12B) Exercise 12.2
1. What is the primary formula used to solve problems in RS Aggarwal Class 7 Maths Exercise 12.2, and how is it rearranged to find the Principal, Rate, or Time?
The core formula for all problems in this exercise is the Simple Interest (S.I.) formula: S.I. = (P × R × T) / 100, where P is Principal, R is Rate of interest per annum, and T is Time in years. To solve for other variables, this formula is rearranged as follows:
To find the Principal (P): P = (100 × S.I.) / (R × T)
To find the Rate (R): R = (100 × S.I.) / (P × T)
To find the Time (T): T = (100 × S.I.) / (P × R)
2. How should you correctly calculate Simple Interest in RS Aggarwal problems when the loan period is given in months or days?
It is crucial to convert the time period into years to use the standard formula, as the interest rate is typically given per annum. For problems in Exercise 12.2, follow this method:
If Time is in months: Convert it to years by dividing by 12. For example, 6 months becomes 6/12 or 0.5 years.
If Time is in days: Convert it to years by dividing by 365. For example, 73 days becomes 73/365 years. The formula then becomes S.I. = (P × R × T) / (100 × 365), where T is the number of days.
3. Why is it essential to convert the time period to years before calculating Simple Interest?
The Rate of Interest (R) in most problems, including those in RS Aggarwal, is specified as 'per annum,' which means 'per year.' To ensure the calculation is accurate, the units for both Rate and Time must be consistent. If you use a rate per year but a time period in months, the resulting interest will be incorrect. Converting the time to years aligns it with the annual rate, making the formula P×R×T work correctly.
4. How do you find the total amount to be repaid for a sum borrowed in Exercise 12.2 problems?
To find the total amount to be repaid, you must first calculate the Simple Interest (S.I.) using the formula S.I. = (P × R × T) / 100. After finding the S.I., you add it back to the original principal amount. The formula is: Amount (A) = Principal (P) + Simple Interest (S.I.). This final value represents the total sum that is due at the end of the loan period.
5. What is the fundamental difference between Simple Interest (used in this chapter) and Compound Interest?
The fundamental difference lies in how the interest is calculated over time. Simple Interest is always calculated on the initial principal amount, regardless of the time period. In contrast, Compound Interest is calculated on the principal amount plus the accumulated interest from previous periods. This is why it is often called 'interest on interest.' Class 7 Maths focuses on Simple Interest to build a solid foundation before introducing the more complex concept of Compound Interest in later classes.
6. What common mistake should be avoided when the values for Principal, Rate, and Time are given in word problems in Exercise 12.2?
A common mistake is incorrectly identifying the given values or failing to ensure the units are consistent. Before applying the formula, always do the following:
Clearly identify which value is the Principal (P), Rate (R), and Time (T).
Check that the Rate is per annum and the Time is in years. If not, perform the necessary conversions (e.g., months to years).
Ensure you are calculating what the question asks for—sometimes it is just the Simple Interest, and other times it is the total Amount (P + S.I.).
