A few math problems, please explain, and offer a reward of fifty well wishers to help

1.Because v= r h

The base area is equal, the ratio of height is 3:5, so the volume ratio is also 3:5 The volume of the second cylinder is 48 3 5 = 80 cubic centimeters.

That is, the second cylinder has a volume of 80-48 = 32 cubic centimeters more than the first.

2.The speed of the car is (390-270) kilometers per hour.

The distance between A and B is (km).

3.A efficiency = 1 20, B efficiency = 1 10, C efficiency = 1 152 (hours) Answer: It will take 2 hours to complete.

Number of cars = number of people - 15

60 * number of cars = number of people + 60

Number of people = 240

The number of cars = 5u is the number of 45 seats; V is the number of 60-seater vehicles.

45*u+60*v>=240

220*U+300*V is the minimum value.

u=4；v=1

Car rental costs 1180

It's not kind to give points.

If the radius of the base surface is equal, the base area is equal.

The volume ratio is equal to the ratio of the high and is 3:5

The second one is 48 3 (5-3) = 32 cubic centimeters more than the first.

12:30 pm to 2:30 pm, a total of 2 hours.

Cars travel per hour (390-270) 2=60 km.

10:00--12:30, a total of hours.

Distance between A and B: 60 km.

1-(1 20+1 15) 6] (1 20+1 10) = 2 hours.

1) Solution: Set a total of x people.

x-15)/45=(x+60)/60

x/45-1/3=x/60+1

1/45-1/60)x=1+1/3

1/180x=4/3

x=240A: There are 240 students in total.

The average price of a 60-seater car is 300 60 = 5 yuan per person.

The average price of a 45-seater car is 220 45 = 4 and 8 9 yuan per person.

240÷45=5...15 people.

Rent 4 45-seater cars, 1 60-seater car rent is the least, 4 220 + 300 = 1180 yuan.

4. (1): The number of cars to be rented is x.

45x+15=60x(x-1) gives x=5

So the number of people = 240 people.

2): 4 cars with 45 seats, 1 car with 60 seats.

a c e is bad=60° and ad=5 if collinear

There's no bounty ghost that will teach you!!

First, the area is the largest, and the two smallest faces should be connected, that is, the two smallest faces are missing. Namely:

8*5+4*5+4*8)*4-4*5*2 328 (square centimeters) is the largest, and the two largest faces should be connected, that is, the two largest faces are missing. Namely:

8*5+4*5+4*8)*4-8*5*2 288 (square centimeters) two, 12 3 4, the side length of the cube is 4, sawn into three to increase 4 faces. Namely:

12 3 4 (small cube side length).

4*4*4 64 (square centimeters).

Third, set the thickness of xm

4*6*x=6

24x=6x=four, (96-10*4) 8 7 (cm) (this is the length of the bottom side) volume: 7*7*10 490 (cubic centimeters).

5. Total volume Truncated volume The remaining volume.

30*20*20 20*20*20 4000 (cubic centimeters).

1.If you want to have the largest surface area, you need to put together the two faces with the smallest area, so the maximum surface area is 2 (8 * 5 + 5 * 4 + 4 * 8) * 2-2 * 5 * 4 = 328, in the same way, if you want to have the smallest surface area, you have to put together the two faces with the largest area, so the minimum surface area is 2 (8 * 5 + 5 * 4 + 4 * 8) * 2-2 * 5 * 8 = 288

2.Because the height is 12, the horizontal saw is exactly three cubes, so the original cuboid is 4 in length and width, and the surface area is 2 (12 * 4 + 4 + 4 * 12) = 224, and the surface area after sawing into three cubes is 3 * 6 * 4 * 4 = 288, so 288-224 = 64 is added

4.Let the length and width of the box be x, (because the bottom is square) so 4*(x+x+10)=96, so x=7, so the volume is 7*7*10=490

5.The largest cube is cut into a cube with an edge length of 20cm, so the remaining cut is 30*20*20-20*20*20=4000cm2

1. It is known that the parabola y=ax 2+(4 3+3a)x+4 intersects with the x-axis at two points a and b, and intersects with the y-axis at the point c, whether there is a real number a, so that abc is a right-angled triangle, if it exists, the value of a is requested, if it does not exist, please explain the reason.

Solution: Exists. y=ax 2+(4 3+3a)x+4 intersects with the y-axis at the point c, then c(0,4).

1) Assuming the parabola opening is upward, a>0, then the intersection of the parabola and the x-axis is on the same side of the y-axis.

then abc cannot be a right triangle.

2) Assuming that the parabola opening is downward, a<0, then the intersection of the parabola and the x-axis is on either side of the y-axis.

Then y=0, the coordinates of a and b are ((-3,0), (4 3a,0), and point c is a right-angle point.

According to the Pythagorean theorem, out a=-1 4<0

So when a=-1, abc is a right triangle.

Forget about it, find the formula, and set it one by one.

37 minutes and 26 seconds x 9 = 171 degrees 333 minutes 234 seconds = 171 degrees 336 minutes 54 seconds.

176 degrees, 36 minutes, 54 seconds.

Degree 39 minutes + 67 degrees 31 minutes - 21 degrees 17 minutes x 5 = 115 degrees 70 minutes - 105 degrees 85 minutes.

114 degrees 130 minutes - 105 degrees 85 minutes.

9 degrees 45 minutes.

degrees - 52 degrees 32 minutes 30 seconds = 106 degrees 59 minutes 60 seconds - 52 degrees 32 minutes 30 seconds = 54 degrees 27 minutes 30 seconds.

48 minutes + 41 degrees 37 minutes = 80 degrees 85 minutes.

81 degrees 25 minutes.

Degrees: 36 minutes, 24 seconds, x 4 = 100 degrees, 144 minutes, 96 seconds = 102 degrees, 25 minutes, 36 seconds.

Degrees 2 minutes divided by 5 = 45 degrees 180 minutes 120 seconds divided by 5 = 9 degrees 36 minutes 24 seconds.

Degree 23 minutes + 4 degrees 56 minutes = 23 degrees 79 minutes.

24 degrees 19 minutes.

Degree 02 minutes - 16 degrees 22 minutes = 55 degrees 62 minutes - 16 degrees 22 minutes = 39 degrees 40 minutes.

degrees - 15 degrees 41 minutes 29 seconds x 3 = 90 degrees - 45 degrees 123 minutes 87 seconds, = 87 degrees 178 minutes 120 seconds - 45 degrees 123 minutes 87 seconds.

42 degrees, 55 minutes, 33 seconds.

Degrees 22 minutes divided by 3 = 132 degrees 141 minutes and 60 seconds divided by 3 = 44 degrees 47 minutes and 20 seconds.

Sky. Sheet.

Ton. I hope my you are satisfied, thanks.