Get on your knees and ask for a math problem! Write down the steps in detail!

The solution is solved by using the volume of the box equal to the base area multiplied by the height.

1) The length is increased by 2 cm, and the volume is increased by 40 cubic centimeters

Width Height (base area) = 40 2 = 20 (square centimeters) 2) The width increases by 3 cm, and the volume increases by 90 cubic centimeters, then:

Length height (base area) = 90 3 = 30 (square centimeters) 3) The height increases by 4 cm, and the volume increases by 96 cubic centimeters, then:

Length and width (base area) = 96 4 = 24 (square centimeters) 4) The surface area of the original cuboid: (20 + 30 + 24) 2 = 148 (square centimeters) Answer: The surface area of the original cuboid is 148 square centimeters.

Width * Height = 40 2 = 20

Length * Height = 90 3 = 30

Length * width = 96 4 = 24

Original surface area (20 30 24) 2 148

Let the length, width and height be x,y,z; The volume is xyz

x+2)yz=xyz+40 to get yz=20

x(y+3)z=zyz+90 gives xz=30

xy(z+4)=xyz+96 gives xy=24

Surface area = 2 (xy + yz + xz) = 2 (20 + 30 + 24) = 148

Set length = x, width = y, height = z

then 2yz=40

3xz=90

4xy=96

i.e. yz=40, xz=90, xy=24

So xy=(40 z)*(90 z)=24 gives z=5 6

Just find xy.

Upper area: 40 4=10 Side area: 20 2=10 Frontal area: 30 3=10

Old and immortal: The surface area is: (10+10+10) 2=60

Let the length, width and height be xyz to get 2yz=40 x3z=90 xy4=96 x 2y 2z 2=20*30*24 to get xyz=120

Let x be long, y be wide, and z be high.

x+2)*y*z-(xyz)=40

x*(y+3)*z-(xyz)=90

x*y*(z+4)-(xyz=96

Simultaneous solution in the calculation is just stupid method.

Set the length, width and height as x, y, and z respectively, and then solve the three equations according to the three conditions of the problem.

Don't be lazy, you have to do it yourself.

Solution: Derive a wide search according to the principle of parallelism.

The angle of reflection of the included and the number of lands through the plane mirror are respectively , and the number of angles of incidence is always equal to the angle of reflection.

Plane carefully complete the reflection angle of the mirror

In opp'The sum of the inner angles is 180°

Solution 9 5-45=100-45=65(km-hour (1+13 14)=540 27 14=280 (person) Boys.

280*13 14=260 (person) Girls.

3. (23+22) 3 10=45 3 10=150 (strain (1-3 5)=100 2 5=250 (yuan) bookshelf 250-100=150 (yuan) bed.

(1).

95 and 241 630

2) Team A, B and C complete 1 10 every day, and Team B and C complete 1 15 2 = 1 30 every day, then Team A completes 1 10-1 30 = 1 15 every day, and because A completes 7 15 more than C, then A completes 7 15 10 = 7 150 more than C in one day, then C completes 1 15-7 150 = 1 50 in one day, then Team B completes 1 30-1 50 = 1 75 every day, then Team B needs 75 days to complete alone.

ab is the diameter.

c=90°od Sakura Filial Piety Banquet BC

dea=90°

d+∠dae=90°

Ridge silver d = bac

bac+∠dae=90°

Ad is the tangent of a semicircle o.

oe‖bc，ao=bo

ae=ce=√2

ac=2√2，ab=2√3

ao=√3∠d=∠bac

RT DAO Shen Peng RT ACB

ad:ac=ao:bc

ad=ao×ac÷bc=√3 ×2√2 ÷2=√6

Calculate the flat of A and B.

Average grade: A's average grade s1 = (8

B's average score s2=(8 3+9 4+10 3) 10=9 means that A belongs to B and B have the same average score, but as can be seen from the graph, B is more stable, because B's results are mainly concentrated in 9 rings, while A's results are good and bad, hovering between 8 and 10.

To solve this kind of problem, we need to use the knowledge of variance, and first calculate the average score of A and B, and the average score of A is x=9

B's average grade x = 9

If the average score is the same, then: variance of A = and variance of B =

So B's grades are stable.

Grades of bai

Stabilization requires the calculation of "variance du":

sA=[4(8-9) zhi2+2(9-9) 2+4(10-9) 2] 10=,sB=[3(8-9) 2+4(9-9) 2+3(10-9) 2] 10=, because the smaller the variance dao, the more stable the score.

The results of B are more stable. Pick B

The average score of A is (4*8+2*9+4*10) 10=9, and the average score of B is (3*8+4*9+3*10) 10=9, so A is as stable as B.

Substitute the value of x,y and get it.

4+m-1=2

m=-12n+1=1

n=0, so (m+n)=-1

So the power of 2010 of (m+n) is equal to 1

x=2, y=1 is the system of equations 2x+(m-1)y=2; nx+y=1.

Then there is 4+m-1=2, m=-1

2n+1=1，n=0

m+n)^2010=1^2010=1