In order to strengthen the macro management of the production and marketing of cigarettes, the state imposes a surtax policy on the sales of cigarettes. Now we know that the market price of a certain brand of cigarettes is 70 yuan. If there is no surtax, the annual production and sales of 1 million cigarettes will be reduced by 10 million cigarettes per year. If the state imposes a surtax and taxes x yuan per 100 yuan (called tax rate X%), the annual production and sales will be reduced by 10 million cigarettes The additional tax is 1.68 million yuan, and the production and sales of cigarettes are under macro control. The annual sales of cigarettes are no more than 500000. What is the tax rate?

In order to strengthen the macro management of the production and marketing of cigarettes, the state imposes a surtax policy on the sales of cigarettes. Now we know that the market price of a certain brand of cigarettes is 70 yuan. If there is no surtax, the annual production and sales of 1 million cigarettes will be reduced by 10 million cigarettes per year. If the state imposes a surtax and taxes x yuan per 100 yuan (called tax rate X%), the annual production and sales will be reduced by 10 million cigarettes The additional tax is 1.68 million yuan, and the production and sales of cigarettes are under macro control. The annual sales of cigarettes are no more than 500000. What is the tax rate?

Quadratic equation of one variable
In the right angle △ ABC, C = 90, AC = 3, BC = 4, point E is on AC, and point F is on AB (points E and F are not coincident with the end points), and the line EF bisects the perimeter and area of the right angle △ ABC at the same time to find the length of AE?

Then AB = 5 (Pythagorean theorem) s △ ABC = 3 * 4 / 2 = 6 let AE = x, AF = y, then: x + y = (3 + 4 + 5) / 2 = 6 (1) [circumference bisection] do FG ⊥ AC in G, then △ ABC ∽ afgfg / BC = AF / AbfG / 4 = Y / 5fg = 4Y / 5S △ AEF = AE * FG / 2 = x (4Y / 5) / 2 = 2XY / 5 = s △ ABC / 2 = 6 / 2 = 3, that is