20% of a man's salary is paid as house rent, 60% is spent on his living expenses and 10% represents his savings.\nIf he spends the remaining Rs. 30 on the education of his children, what is his total monthly salary?

Introduction / Context:
This question tests your understanding of percentage allocation of income along with a small fixed amount spent on an extra category. The man's salary is divided into percentages for rent, living expenses, and savings, and the remaining part is given as a specific rupee amount for education. You must use these pieces of information to recover the total salary.

Given Data / Assumptions:

• Let the man's salary be S rupees.
• 20% of S is spent on house rent.
• 60% of S is spent on living expenses.
• 10% of S is saved.
• The remaining amount, spent on children's education, equals Rs. 30.
• All percentages are based on the total salary S.

Concept / Approach:
First, we note that 20% + 60% + 10% = 90% of the salary is accounted for by rent, living expenses, and savings. The remaining part of the salary is 10% (because 100% − 90% = 10%). We are told that this remaining part is Rs. 30, so 10% of S equals 30. This directly allows us to solve for S using a simple percentage equation.

Step-by-Step Solution:
Step 1: Total salary = S. Step 2: Percentages: 20% for rent, 60% for living, 10% for savings. Total accounted percentage = 20% + 60% + 10% = 90%. Step 3: Remaining percentage of salary = 100% − 90% = 10%. Step 4: This remaining 10% of S is spent on education, and is given to be Rs. 30. Step 5: Write the equation: 10% of S = 30, or (10 / 100) * S = 30. Step 6: Simplify: 0.10S = 30. Step 7: Solve for S: S = 30 / 0.10 = 300. Step 8: Therefore, the man's monthly salary is Rs. 300.

Verification / Alternative check:
Check that the distribution matches the problem statement for S = 300. Rent = 20% of 300 = 0.20 * 300 = 60. Living expenses = 60% of 300 = 0.60 * 300 = 180. Savings = 10% of 300 = 30. Total of these three = 60 + 180 + 30 = 270. Remaining amount for education = 300 − 270 = 30, which matches the given figure. Thus the salary of Rs. 300 is consistent.

Why Other Options Are Wrong:
900, 3000, 9000, 600: For each of these salary values, 10% would not equal 30. For example, 10% of 900 is 90, and 10% of 3000 is 300, both of which conflict with the given information that the remaining amount is Rs. 30.

Common Pitfalls:
Some students incorrectly try to calculate each category in rupees first without setting up a clear equation, which can lead to confusion. Others treat the Rs. 30 as an additional percentage value instead of a fixed remainder. The simplest and safest method is to observe that the percentages sum to 90% and then directly equate the remaining 10% to 30.

Final Answer:
The man's total monthly salary is Rs. 300.