The second order equation of one variable The average selling price of a newly listed fruit sold by a fruit dealer last month was 10 yuan / kg, and the monthly sales volume was 1000 kg. After market research, if the price of this kind of fruit was adjusted to X Yuan / kg, the functional relationship between the sales volume of this month y (kg) and X (yuan / kg) was y = - 1000x + 9000 It is known that the cost price of the fruit in last month was 5 yuan / kg. When the cost price in this month is 4 yuan / kg, in order to increase the profit of the fruit in this month by 20% compared with that in last month, and at the same time to make customers get benefits, how much should the price of the fruit be reduced to per kg?

The second order equation of one variable The average selling price of a newly listed fruit sold by a fruit dealer last month was 10 yuan / kg, and the monthly sales volume was 1000 kg. After market research, if the price of this kind of fruit was adjusted to X Yuan / kg, the functional relationship between the sales volume of this month y (kg) and X (yuan / kg) was y = - 1000x + 9000 It is known that the cost price of the fruit in last month was 5 yuan / kg. When the cost price in this month is 4 yuan / kg, in order to increase the profit of the fruit in this month by 20% compared with that in last month, and at the same time to make customers get benefits, how much should the price of the fruit be reduced to per kg?

Suppose that the price of this kind of fruit should be reduced to x yuan per kilogram
(X-4) (-1000X+9000)=(1+20%)(10-5)×1000
The solution is x = 6 or x = 7
To make the customers get benefits ﹣ x = 6
The price of this kind of fruit should be reduced to 6 yuan per kilogram