To find the man's average monthly income, let's first break down the information given:

1. Expenditure for the first 5 months:

The man's average expenditure for the first 5 months is Rs. 120 per month. So, his total expenditure for these 5 months is: $\text{Total expenditure for first 5 months} = 120 \times 5 = 600 \, \text{Rs.}$

2. Expenditure for the next 7 months:

His average expenditure for the next 7 months is Rs. 130 per month. So, his total expenditure for these 7 months is: $\text{Total expenditure for next 7 months} = 130 \times 7 = 910 \, \text{Rs.}$

3. Total expenditure for the year:

Now, the total expenditure for the entire year (12 months) is the sum of the expenditures for the two periods: $\text{Total expenditure for the year} = 600 + 910 = 1510 \, \text{Rs.}$

4. Savings for the year:

He saves Rs. 290 during the year.

5. Total income for the year:

The total income for the year is the sum of his total expenditure and his savings: $\text{Total income for the year} = 1510 + 290 = 1800 \, \text{Rs.}$

6. Average monthly income:

To find his average monthly income, divide the total income for the year by 12 (since there are 12 months in a year): $\text{Average monthly income} = \frac{1800}{12} = 150 \, \text{Rs.}$

Thus, his average monthly income is Rs. 150.

Would you like more details on any of the steps? Here are 5 related questions:

1. How can you calculate average expenditure over a period?
2. If his expenditure had been Rs. 140 for the last 7 months, how would the average income change?
3. What is the formula for calculating total income based on expenditure and savings?
4. How do savings impact average income calculation?
5. How does changing the number of months affect the average calculation?

Tip: Always break down problems into smaller parts to avoid errors and make calculations easier.