Math masters, please enter... Hurry Fast Primary .

One. Square kilometre = (20) hectares.

Two. Judging that the year 2100 is a leap year. (False) 2100 400= A leap year is calculated by dividing the number of whole centuries by 400.

Three. 1.If seedlings are planted according to the plant spacing of 1 dm and the row spacing is 15 cm, how many seedlings can be planted in a 6-hectare paddy field?

Solution: 1 dm 10 cm.

10*15 150 square centimeters.

12 hectares 1200000000 square centimeters.

1200000000 150 8000000 A: A 12-hectare paddy field can plant 8000000 seedlings 2The railway from A to B is 675 kilometers long, and one train starts at 5 p.m. on the first day

30From A to B, the average train travels about 45 kilometers per hour, when does the train arrive at B?

675 45 = 15 hours at half past eight in the morning the next day.

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1 20 hectares.

2 pairs. 3 16,000,000 plants at 8:30 a.m. the next day.

No. The question is a bit problematic.

675 45 = 15 hours 17:30 + 15 = 32:30-24 = 8:30 the next day

1. 1 square kilometer = 1,000,000 square meters, 1 hectare = 10,000 square meters, 1 square kilometer = 100 hectares, so hectares.

Second, I checked that 2100 is not a leap year!!

3. Square meters = 100 square decimeters, 1 hectare = 10,000 square meters, 60,000 (plants.

hours, 8:30 a.m. the next day.

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Excuse me, the farmer died with 15 cows.

The wife gave half of all the oxen, plus half a head.8

The eldest son gave half of the remaining cattle and half a head.4

The second son gave half of the remaining oxen, plus half a head.2

The eldest daughter is given to the remaining half plus half of the head1

As a result, not a single cow died, and there was not a single cow left, and it was just finished.

A did it for 2 days, B did it for 3 days, and the total number of 1 2 could be completed

A did 1 day, B did 2 days, 7 24 of the total number can be completed, and it takes a few days for A and B to do it: 2x+3y=1 2

x+2y=7/24

x=1/8y=1/12

1/（x+y）=24/5

1. Find the definition domain of the following function.

1）f（x)=1/4x+7

x≠02)f(x) = 1-x + x+3 -11-x 0 and x+3 0, so -3 x 1

2. The known function f(x)=3x 3+2x

f(2)=3*2^3+2*2=24+4=28f(-2)=3*(-2)^3+2*(-2)=-24-4=-28f(2)+f(-2)=28-28=0

f(a)=3a^3+2a

f(-a)=-3a^3-2a

f(a)+f(-a)=3a^3+2a-3a^3-2a=0

1.The average speed is 20 2 = 10 m s

Time 25 10=

2.It was used from 20m s to 0, a decrease of 20 per second

3.Set t seconds, the speed is 20-8t when rolling to 15 meters, the average speed is (20+20-8t) 2=20-4t, rolling 15m distance (20-4t), t=15 t=(5- 10) 2t is approximately equal.

Think of the motion of the ball as a uniform deceleration motion.

The average velocity is (5+0) 2=

Time 10 The average speed of the ball per second decreases (5-0) 4=

It took x seconds to move to 5 meters.

5+x1=4+2√2 x2=4-√2

According to the actual problem, x1 is rounded and x2 is taken

Therefore, (4- 2) seconds = seconds.

s = vo·t + a·t 2, vt - vo = a·t where s=25, vo=20, vt=0 so the solution is t=

a=-8 (m/s²）

Thus, 1The ball rolled for a second, 2The speed of the ball is reduced by an average of 8 meters per second.

20·t1 - 8·t1²/2

The solution yields t1=(5-10) 2

The initial velocity v0=20m s s=v0t-1 2at2 and the end velocity is 0, then 0=v0-at then two unknowns and two equations can be solved a and t.

The second question is the value of a in the deceleration motion where a=8m s2 t=when rolling to 15 meters, s=15=v0t-1 2at2 knows v0,a, then t= or t=rounding" is obtained and the final t=0

Solution: 1) AC is the diagonal of the quadrilateral ABCD, which in turn is a square.

acd=45°

DC be

dce=90°

ACE= ACD+ DCE=90°+45°=135°2) According to the Pythagorean theorem, AC=AB+BC quadrilateral ABCD is a square.

ab=bc=cd=da=4cm

It can be solved that AC= (4 +4 )=4 2 ( is the root number) of the triangle ace with ce as the base edge and a as the vertex, then the height and length on the ce side is the length of ab ce=acce=4 2

According to the formula for the area of the triangular clump: (base height) 2

It can be regarded as a stuffy Zheng jujube.

ace=（ce×ab）/2=（4√2×4）/2=8√2

First question: Because abc= odc=90So 2= a=60, and aob=90, so lead Hu abo=30 degrees, bod=90- 1=30 degrees.

The second question: the distance from point b to ac is bo=24 5The distance from point A to BC is ab=6, and the distance from point C to Huai collapse block AB is shirt without BC=8

Thank you!!!

The main thing is that there is a conclusion that the ratio of the center of gravity to the midline is 2:1

So af:fc=2:1

ef：bc=ag：ad=2:3

1 * number of days per day = 120 * 1 8 * 7 = 105 pages 2 the first time + the second time = 3 2 * 1 4 + 3 4 = 9 8 square meters.

3 Transported = 72 * (1-1 9) = 64 tons, each car = 64 16 = 4 tons.

1.Solution: 120 * 1 8) *7

105 (pages).

A: I can read 105 pages a week.

2.Solution: (3 2) *1 4) +3 4) = (3 8) +3 4).

9 8 (sqm).

A: I looked at 9 to 8 square meters.

3.Solution: 73 * 1-1 9) 16 = 73 * 8 9) 16

4 (tons) A: The average cargo per vehicle is 4 tons.