Aakash bought a mobile worth Rs 12000 and paid a rent of Rs 9000 from his salary. If he used `70%` of the monthly salary for buying mobile and paying rent then find his monthly salary.

Options

A. Rs 20000
B. Rs 21000
C. Rs 79000
D. Rs 30000

Answer

To find Aakash's monthly salary, we can follow these steps:

1. **Identify the total amount spent**: Aakash bought a mobile for Rs 12,000 and paid a rent of Rs 9,000. We need to add these two amounts together to find out how much he spent in total.

\[ \text{Total amount spent} = \text{Cost of mobile} + \text{Rent} = 12000 + 9000 = 21000 \]

2. **Set up the equation based on the percentage of salary used**: According to the problem, Aakash used 70% of his monthly salary for these expenses. Let his monthly salary be represented by \( S \). Therefore, we can express this as:

\[ 0.7S = 21000 \]

3. **Solve for the monthly salary \( S \)**: To find \( S \), we need to divide both sides of the equation by 0.7.

\[ S = \frac{21000}{0.7} \]

Performing the division:

\[ S = 30000 \]

4. **Conclusion**: Aakash's monthly salary is Rs 30,000.

### Summary of Steps:
1. Calculate total expenses (mobile + rent).
2. Set up the equation for the percentage of salary used.
3. Solve for the monthly salary.