Help solve 3 math problems, thank you.

1.The Limin Grain Station brought back a batch of flour. Sell 70%. Another 900kg was brought back, and the flour in the grain store was 105% of the original flour. How many kilograms of flour did the grain store have?

Answer: If there was mkg before, then there is:

m(1-70%)+900=105%m, i.e., m=1200kg

1.If the original flour x kg of the grain store is set up, the solution is x = 1200

2.If there are x tons of coal in pile B, then there are 3 4x tons of coal in pile A.

So we get 3 16x+x=95 and get x=80

3.=-sin690+cos750

sin(2·360-30)+cos(2·360+30)1 2+root:3 2

1 + followed by 3 2

tan 2(180) = tan (180) 2 = 0 The third trigonometric function is not understood.

cos0=1

cos0=1

sin180=0

I didn't understand the fourth trigonometric function.

1 10 people, each five meters apart, make up nine five meters in length.

Except for 4 minutes to get meters.

2 40 9 * 21 + 40 9 * 24 = 200 (square centimeters) 3 60 Gu Xi refers to 70 Qianlong said that two sixties and three into seven = 141 Ji Xiaolan said two 70 and 1 is also 141

The result was 141 high life.

Because of the time issue, I will only answer the first question: 1Because everyone's bridge crossing speed is the same, the speed is calculated first.

Divide the distance by the time of 4min; 2.Don't pay attention to the first person, let's look at the distance of the last person, because there are 10 people, the distance is 5 meters, so the distance of the last person is; 3.Know the speed and distance, find the time!

In fact, the question is quite test-taking, just see it clearly! There may be miscalculations, pure hand calculations!

1. What is the speed ...... talk about?

Cm. Year.

The length of the human contingent is 45 meters. How do you ask for speed without speed?

3.Not really.

1. The total electricity cost of Xiao Ming's household = yuan.

Average electricity cost per person = RMB.

2. The speed of the aircraft = 1650 km h.

The speed of the airplane is the speed of the train = 750 150 = 5 times.

3. The number of floor tiles required is:

Requires 345 blocks.

1. (85*RMB).

km/h. 750 150 = 5 (times).

3. Square meters.

square meters) blocks.

=50 (person).

Solution: The total number of people is: 60 40 100 (people).

100 people are distributed in a ratio of 8:7:5 as:

40, 35, 25.

So there are 60 40 20 (people) in Village A who are building roads for Village C.

There are 40 35 5 (people) in Village B who are building roads for Village C.

Therefore, the people who build roads for village C in village A should be paid:

1350 20 25 1080 (yuan).

The wages of those who build roads for village B for village C are due:

1350 5 25 270 (yuan).

Answer: Village A should get 1,080 yuan, and village B should get 270 yuan (40 is the number of people in village B).

Solution:1The function relation is:

y=-10x+10002.The function relationship is: y=-10x*x+1400x-400003

By the previous profit function relation: y=-10x*x+1400x-40000a<0, the function is the maximum, x=-b 2a=1400 20=70, so when the selling price is 70 yuan, the profit is the largest.