The cost price of a fridge is Rs. 1000. A dealer marked it up at Rs. ‘x’ above its cost price and offered ‘r%’ discount on the marked price. If he earned 20% profit then find the value of ‘x’.
I. A sum of Rs. 4000 amounts to Rs. 5000 after 1 year at r% rate of compound interest.
II. r = 25%
III. 1000r + xr = 40000

ATQ, CP = 1000, MP = 1000 + x SP = 1000 × 6/5 = 1200 = (1000 + x) × (100 − r)/100 ----Equation 1 From I, We can determine r from the compound interest relation: 4000 becomes 5000 in 1 year at r% CI, so r is known. Using that r in equation 1, we can calculate x. So I alone is sufficient. From II, r = 25% is directly given. Putting r = 25 in equation 1, we get: 1200 = (1000 + x) × 75/100 (1000 + x) = 1200 × 100/75 = 1600 x = 1600 − 1000 = 600 So II alone is sufficient. From III, 1000r + xr = 40000 r(1000 + x) = 40000 (r/100)(1000 + x) = 40000/100 = 400 So, 400 is the discount on MP. Discount on MP = MP − SP = (1000 + x) − 1200 So, (1000 + x) − 1200 = 400 1000 + x = 1600 x = 600 Thus, III alone is sufficient. Thus, I, II & III are alone sufficient to answer the question.