A man’s pension on retirement from service is equal to half the average salary during last 3 years of his service. His salary from 1-1-1983 is Rs. 380 per month with increment of Rs. 40 due on 1-10-83, 1-10-84 and 1-10-85, If he retires on 1-1-86, what pension does he draw ?

annual salary of man for the year 1983 = 380*9 (for first 9 months) + 420*3 (for last 3 months after increment) = 3420+1260 = rs 4680

similarly,annual salary of man for the year 1984 = 420*9 + 460*3 = rs 5160

similarly,annual salary of man for the year 1985 = 460*9 + 500*3 = rs 5640

avg monthly salary of man for last 3 years = $$\frac{4680+5160+5640}{36}$$ = 430

pension of the man is = $$\frac{430}{2}$$ = 215