After practice, Ding Ding wrote 15 more words per minute than before. It is known that Ding Ding now writes twice as many words per minute as before. How many words per minute did he write?

After practice, Ding Ding wrote 15 more words per minute than before. It is known that Ding Ding now writes twice as many words per minute as before. How many words per minute did he write?

15 ÷ (2-1) = 15

Mathematical problem of first order function
There are 300 tons of fertilizer in city a and 200 tons of materials in city B. now all these fertilizers are transported to villages C and D. the cost of transporting fertilizer from city a to villages C and D is 20 yuan and 25 tons respectively; the cost of transporting materials from city B to villages C and D is 15 yuan and 24 yuan per ton respectively?
Township D needs 260 tons of fertilizer

If a-cx ton is set, then: because city a has 200 tons of fertilizer: A-D, 200-x tons. Because Township C needs 240 tons: B-C, 240-x tons. Because Township D needs 260 tons: B-D, 260-200 + X tons. Then, the transportation costs are: a-c 20xa-d 25 (200-x) B-C 15 (240-x) B-D 24 (6

After the "5 · 12" Wenchuan earthquake, a fitness equipment sales company donated all the sales profits in May to the disaster area through the local "Red Cross Society". It is known that the company only sold a number of a, B and C types of equipment in May, and each type of equipment is no less than 8. The expenses in may include the purchase price of this batch of equipment of 640000 yuan and other expenses (including employees) The purchase price and selling price of these three kinds of equipment are shown in the table below. The relationship between the personnel salary Y1 (10000 yuan) and the miscellaneous expenses Y2 (10000 yuan) and the total sales volume x (sets) is a linear function (as shown in the figure) (1) find the function analytic formula of Y1 and X; (2) find the total sales volume of the company in May; (3) set up the company to sell T sets of type a equipment in May The sales profit is w (ten thousand yuan), find the functional relationship between W and T; (sales profit = sales - purchase price - other expenses) (4) please guess the maximum amount of the company's donation to the disaster area this time. The purchase price of model a, B and C (ten thousand yuan per set) is 0.91.21.1, and the selling price (ten thousand yuan per set) is 1.21.61.3

(1) Let the analytic formula of Y1 and X be Y1 = KX + B. according to the meaning of the problem, we get b = 0.220k + B = 1.2, and the solution is k = 0.05b = 0.2. The relationship between Y1 and X is Y1 = 0.05x + 0.2 (2). According to the meaning of the problem, we get: Y1 + y2 = 0.05x + 0.2 + 0.005x + 0.3 = 3.8, and the solution is: x = 60. The total sales volume of the company in May is 60 sets