The first year, two cows produced 8100 litres of milk. The second year their production increased by 15% and 10% respectively, and the total amount of milk increased to 9100 litres a year. How many litres were milked from each cow each year?
Answers.
A) 3472  B) 8222  C) 4370  D) 26777  E) 8222

Rationale: let x be the amount of milk the first cow produced during the first year . then the second cow produced ( 8100 − x ) ( 8100 − x ) litres of milk that year . the second year , each cow produced the same amount of milk as they did the first year plus the increase of 15 % 15 % or 10 % 10 % . so 8100 + 15100 ⋅ x + 10100 ⋅ ( 8100 − x ) = 91008100 + 15100 ⋅ x + 10100 ⋅ ( 8100 − x ) = 9100 therefore 8100 + 320 x + 110 ( 8100 − x ) = 91008100 + 320 x + 110 ( 8100 − x ) = 9100 120 x = 190120 x = 190 x = 3800 x = 3800 therefore , the cows produced 3800 and 4300 litres of milk the first year , and 4370 and 4730 litres of milk the second year , respectively . answer : c
Answer: C