After 70% of a pile of coal is used up, 180 tons of coal is transported in. At this time, it is 10% more than the original. How many tons of coal is this pile?

70% and 1-70% = 30%
Now it's 1 + 10% = 1.1
So the original 180 (1.1-30%) = 225 tons

If positive numbers a and B satisfy AB = a + B + 3, then the value range of AB is ()
A. [6，+∞）B. [9，+∞）C. （-∞，9]D. （-∞，6]

∵ a, B are positive numbers ∵ a + B ≥ 2Ab ∵ AB = a + B + 3 ∵ ab ≥ 2Ab + 3, let AB = t (t ≥ 0), then t2-2t-3 ≥ 0, the solution is t ≥ 3 or t ≤ - 1 ∵ ab ≥ 9, so B is chosen

A batch of goods was distributed to Party A and Party B at a ratio of 5:3. Party a completed 45% of its task, and the rest was transported to Party B. Party B transported a total of 48 tons. How many tons are there in total?

Suppose that there are x tons of goods in total, then the task of team a is 58x tons, and that of team B is 38x tons. The unfinished task of team a is 58x × (1-45) tons. According to the meaning of the question, we can get the equation: 58x × (1-45) + 38x = 48. Solving this equation, we can get x = 96. A: there are 96 tons of goods in total

If the inequality | x-4 | - | x-3 | > m has a solution, then the value range of real number m is______ ．

∵ the inequality | x-4 | - | x-3 | > m on X has a solution, | x-4 | - | x-3 | denotes the distance from X to 4 on the number axis minus the distance from X to 3, and the maximum distance is 1, so m < 1, so the answer is: (- ∞, 1)

The distance between a and B is 336 km. A car can complete the whole journey in 2.8 hours and a bus can complete the whole journey in 3.5 hours. The speed of a car is faster than that of a bus
How many kilometers per hour is your speed?

Fast = 336 △ 2.8-336 △ 3.5 = 24 km / h

Application of plane vector in solving oblique triangle
It is known that the distance between a and B is 100 nautical miles, and B is 30 degrees north by east of A. ship a sails from point a at a speed of 50 nautical miles per hour to point B, while ship B sails from point B at a speed of 30 nautical miles per hour along the direction of 30 degrees south by East. How long does it take to sail? The distance between the two ships is the shortest

Let the sailing time be x hours, and the distance between the two ships is the shortest. First, draw a diagram, and the angle between the two ships is 60 degrees. Let ship a be at point C after X hours, and ship B be at point D, so that CD & sup2; can be minimized. From the cosine theorem, CD & sup2; = BC & sup2; + BD & sup2; - 2 | BC | BD | CoSb = (100-50x) & sup2

Party A and Party B take out the same amount of money to buy a basket of apples. If Party B pays party a 5.70 yuan, Party A can get 12 kg and Party B can get 18 kg, then how much is the apple per kg?

6 = 0.95 yuan a: 0.95 yuan per kilogram of apples

If - 1 + 3I / 1 + 2I = a + bi (a, B are real numbers), then the value of A-B is

-1+3i/1+2i
=(-1+3i)(1-2i)/(1+2i)(1-2i)
=(5+i)/5
=1+1/5i
=a+bi
a=1 b=1/5
a-b=4/5

A and B race along the 400 meter circular runway (in the same direction). B walks 100 meters per minute. A's speed is 1.25 times that of B, and now
A is 100 meters in front of B. how many minutes later will the two meet?

Let's meet in X minutes
100×1.25x－300＝100x
25x＝300
x＝12

If we know that cosa = 3 / 5, a belongs to (3 groups / 2,2 groups), we can find sin2a-cos2a

Because cos a = 3 / 5, a belongs to (3 / 2,2)
So Sina = - 4 / 5
sin2A-cos2A=2sinAcosA-(2cosA^2-1)
=2sinAcosA+1-2cosA^2
=(sinA+cosA)^2-2cosA^2
=(-4/5+3/5)^2-2*3/5^2=-17/25

After 70% of a pile of coal is used up, 180 tons of coal is transported in. At this time, it is 10% more than the original. How many tons of coal is this pile?