Ratio of price of Black pen and Red pen is 9:5 for

Solution

Let the price of Black pen and Red pen for shopkeeper A is Rs.9 and Rs.5 respectively. Price of Black pen for shopkeeper A = 150 × 9 = Rs.1350 Price of Red pen for shopkeeper A = 50 × 5 = Rs.250 Total price for shopkeeper A = 1350 + 250 = Rs.1600 Here, 1600 ----- 800 => SP of Red pen = (800/1600) × 5 = 2.5 => SP of Black pen = (800/1600) × 9 = 4.5 Price of Red pen sold by shopkeeper D = (2/3) × 4.5 = Rs.3 Unsold pens of B = 25% of 600 = 150 Red pens sold by D = (5/6) × 150 = 125 Black pens sold by D = (1/6) × 150 = 25 Total collection of D by selling Red pens = 125 × 3 = Rs.375