The cost price of a laptop is Rs. 900. Arvind marked it up at Rs. ‘x’ above its cost price and offered ‘r%’ discount on the marked price. If he earned 25% profit then find the value of ‘x’.
I. A sum of Rs. 8000 amounts to Rs. 12500 after 2 years at r% rate of compound interest.
II. r = 25%
III. 900r + xr = 37500

ATQ, CP = 900, MP = 900 + x SP = 900 × 5/4 = 1125 = (900 + x) × (100 − r)/100 ----Equation 1 From I, We can determine the value of r by using the compound interest formula: 8000 becomes 12500 in 2 years at r% CI, so r can be found. Putting this value of r into equation 1, we can obtain x. So I alone is sufficient. From II, r = 25% is directly given. Putting r = 25 in equation 1, we get: 1125 = (900 + x) × 75/100 (900 + x) = 1125 × 100/75 = 1500 x = 1500 − 900 = 600 So II alone is sufficient. From III, 900r + xr = 37500 r(900 + x) = 37500 (r/100)(900 + x) = 37500/100 = 375 So, 375 is the discount on MP. Discount on MP = MP − SP = (900 + x) − 1125 So, (900 + x) − 1125 = 375 900 + x = 1500 x = 600 Thus, III alone is sufficient. Thus, I, II & III are alone sufficient to answer the question.