Two persons A and B started working for a company in

Solution

. A's salary as of 1 Jan 1990 is Rs 400 per month. His increment in his monthly salary is Rs 50 per annum. His total salary from 1 Jan 1990 to 31st Dec 1994 By the formula of AP S = n/2 [2a + (n-1) d], where n = 5 years, a = 400 and d = 50 =12[2(400) +(5−1)50] ×5/2 =12×2500 =Rs 30000 B's salary as of Jan 1st, 1990, is Rs 500 and his half-yearly increment in his monthly salary is Rs 20. His total salary from 1 Jan 1990 to Dec 31, 1994 = 2[2(500) +(10−1)20] ×10/2 =2× [1000+180] ×5 =2×5900 =Rs 11800 Since these are monthly salaries, we need to multiply by 6 (since it is bi-annual): Total salary of B over 5 years=11800×6=35400 Total salary of A and B in the 4-year period: = Rs. 30000 + Rs. 35400 ⇒ Rs 65400