A man spends Rs. 1600 per month on an average for the first three months, Rs 1550 for next four months and Rs. 1800 per month for the last five months and saves Rs 5200 a year What is his average monthly income?

Solution:
Total expenditure for the first 3 months = 3 X 1600
                                                           = 4800
Total expenditure for 4 months = 4 X 1550
                                               = 6200
Total expenditure for 5 months = 5 X 1800
                                               = 9000
Total expenditure and saving (which is income for one year)
= 4800 + 6200 + 9000 + 5200 = Rs. 25200
So, Average monthly income  = 25200/12
                                             = Rs. 2100