Passage

Directions: Study the following data carefully and answer the question that follows. A dishonest petrol dealer mixed some kerosene in petrol and sold it to three customers, P, Q, and R, in the same order. After mixing, the ratio of petrol to kerosene became 9:2, respectively. The table below shows how the exchange took place (The dealer sold 220 litres to person P and then he added 80 litres of petrol and 40 litres of kerosene. The same is given for Q and R). Customers Quantity sold (I) Petrol added (I) Kerosene added (I) Mixture left (I) P 220 80 40 1000 Q y 36 34 M R 260 25r 5r z

If the ratio of petrol to kerosene with the dealer just before selling to R is 10:3, then find the quantity of mixture the dealer has just before selling it to R.

From the previous step, the dealer has 1000 litres with 900 litres of petrol and 100 litres of kerosene before selling to Q. After selling an unknown quantity y of this 9:2 mixture and then adding 36 litres of petrol and 34 litres of kerosene, the dealer has M litres left. Since the ratio just before selling to R is 10:3, the equation (900 minus 9y/11 plus 36) divided by (100 minus 2y/11 plus 34) equals 10/3 is formed. Solving 3 times (936 minus 9y/11) equals 10 times (134 minus 2y/11) gives 2808 minus 27y/11 equal to 1340 minus 20y/11, which results in y = 1320/7 litres. Substituting y back into M = 1000 minus y plus 70 gives M = 650 litres.

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