Math problems! Top Scholars! Help me!

Hehe, you're doing your homework.

Subtract 2 to get 4, -7 times 4 to get -28, -28 plus 4 to get 8, -7 to add 4 to get -3, 8 times -3 to get -24

It's so simple.

Now you know two things.

1. When the speed is 10km, arrive at 10 o'clock in the morning.

2. When the speed is 15km, it arrives at 9 o'clock in the morning.

In other words, when the speed is 15km, it can arrive 1 hour earlier.

Suppose that 10km per hour takes x hours to arrive, then 15km per hour takes (x-1) hours to arrive.

10x=15(x-1)

10x=15x-15

x=3So: the total distance is: 3 10=30

The distance from the school to the museum is x km.

x/10-x/15=10-9

x=30

30 km!

Solution: If it takes X hours for Little A to ride from school to the museum, then it takes (X-1) hours for Little B to ride from school to the museum.

So 10x=15(x-1).

Solution: x=3

So the distance from the school to the museum is s=vt=10*3=30 (km).

The distance from the school to the museum is Y km, and the first time is x hours, and the second time is x - 1 hour.

It is derived from the title, y=10x

y=15(x-1)

From the above two equations, we get y=30

If it takes 10 kilometers per hour to complete the journey, then it takes 15 kilometers per hour and takes x-1 hour, and the equation is obtained

10x=15(x-1)

Solution: x=3

So, the road from the school to the museum is 10*3=30 km.

Yan Xiaoxi, hello:

Solution: The distance from the school to the museum is x kilometers.

x/10－x/15＝10－9

x/10－x/15＝1

3x－2x＝30

x＝30

Channel length: 4 (1-3 5-1 5).

20 km. 1) Inner radius: 16, 2, 8 meters.

Outer radius: 8+2 10 meters.

Size: sqm.

157 lamps.

The length of this canal: 4000 (1-3 5-1 5) = 4000 1 5 = 4000 5 = 20000 (m).

1) Path area: [2+(16 2)] square meters).

2) To install street lights: [(16+2 2) pcs].

(i) The remainder divided by the total is equal to the total: 4 1-3 5-1 5) = 20 (km).

2) Find the outer diameter of the path (16+2x2)=20 (meters).

Then divide the perimeter by the distance of the lamp equal to the number of lamps).

First question:

Set this aqueduct x kilometers, then.

Solution x=20

20 km of canals.

Second question:

I use pi instead.

That's about 157 lights.

4000 * 5 = 20000 meters (a total of 4 5 was dug in the first two days, so 1 5 is left in the end, the length is 4000, 1 5 * x = 4000).

16+4)*Note that because it is the outer edge, it is necessary to divide the outermost circumference by 2 meters, and the width of the road is 2 meters, and the outermost diameter should be added by two 2 meters).

Question adds: (1) What is the relationship between PE, PF and AB? And why!

2) At what position is the point p, is the graph axisymmetric? This shows that the quadrilateral AEPF is very graphic.

1) There is a proportional relationship, which proves that the triangle abc, fbp, and epc are similar and ab=ac is isosceles, then fb=fp, ep=ec

pe:pf:ab=pc:pb:bc

2) When P is the midpoint of AB, AP is axisymmetric.

AEPF is diamond-shaped because the triangle EPC and FBP are equal; E and f are obtained from the median line of the triangle, which are the midpoints of ac and ab, respectively. ep=fp=1/2ab=1/2ac

This is probably a very common problem in junior high school math. This is also asked here, I guess you didn't think about it at all, and we just asked us to help you do your homework. But I'll give you some hints:

1. Interest = principal x interest rate.

2. Speed = distance time.

3. Volume = side length x edge length x edge length.

1 cubic millimeter = 1 mm x 1 mm x 1 mm.

1 cubic nanometer = 1 nanometer x 1 nanometer x 1 nanometer.

1. 10,500 + 12,000 = 22,500 yuan.

Second, scientific notation has been forgotten.

Three, 10 to the 18th power.

You shouldn't be in a hurry if you don't have such a basic question, but you don't.

Anyway, 3 7*x+2=(4 7*x-2)*3 2 There is a mistake in the problem, and there is no solution (you see if you have copied the wrong question).

That is, the lower layer +4 = 107, so the original lower layer is 103, and the upper layer 317 is the standard time faster than his clock (2 58), so after 29 hours, it is faster than 2 * 29 58 = 1 (hour), and the standard time is 6 o'clock.