Two elementary school math problems! Math masters, please fast forward!!

Tree. Since the number of trees planted by the first student is 1 2 of the other three, the number of trees accounted for 1 3 of the total can be found for the other two 1 4 and 1 5 of the total

So the fourth place accounts for 13 60 of the total

So the total is 60

2.The minute hand travels 6 degrees per minute and the hour hand travels 1 2 degrees per minute.

180 (6-1 2) = 360 11 points, so it is 9:33.

The first bit x=1 2(y+z+q).

The second digit y=1 3(x+z+q).

The third digit z=1 4(x+y+q).

q=14 can be solved for xyz q

1. The first, second, and third students planted x, y, and z trees respectively, and the agenda formula can be listed according to the known conditions

x=1/2(y+z+13) ①

y=1/3(x+z+13) ②

z=1/4(x+y+13) ③

Subtract to get x=4 3y

Subtract to get z=4 5y

Substituting into each of them, we can calculate y=15

Then x=20, z=12

The total number is 60.

2. Because walking a circle in a minute is 60 minutes, that is, walking 6 degrees in a minute, and walking a circle on the hour hand is 720 minutes (the time of a day), that is, walking in one minute.

After 9 o'clock it becomes 90 degrees, and it is only possible after 9:30 o'clock, and it is set to 90 degrees after 9 o'clock x minutes.

270 degrees + degrees * x 90 degrees + 6 degrees * x

x=360/11

It is about 33, which is 90 degrees at 9:33.

The first person planted 1 3 of the total, the second planted 1 4 of the total, the third planted 1 5 of the total, and the first three planted a total of 47 60, so the fourth student planted 13 60 of the total, because he planted 13 trees, so the total number was 60.

2 What is the hour and minute hand at right angles to the hour hand? Nine o'clock is not included.

Do it yourself! Develop the development of intelligence.

100 (5 200) = 4000 tails.

Later, there were 5 marked ones in the 200 tails.

It shows that there are about 5 200 = 1 40 of the total number of marked ones, and there are 100 known marked ones.

The total is about 100 1 40 = 4000.

A group of fish were raised in the fish pond, 100 were caught for the first time, and they were marked and put back into the fish pond, and a few months later, 200 fish were caught, and a total of 5 were found. How many fish were there in the pond on the second catch?

100/x=5/200

The solution is x=4000

There are about 4000 tails.

Answer: 2000.

Explanation: Because there are already 100 marked fish in the pond, and for fishing after a few months, the probability of not catching the marked fish is the same, and the probability value = the number of marked fish in the pond = the number of marked fish caught the second time The number of fish caught the second time = 5 200

So the total number of fish in the pond is 100*20=2000

200/（5/100）=4000

A: There were about 4,000 fish in the pond during the second fishing.

However, according to the meaning of the title, you can find the bottom area of the pencil = 9 18 = square centimeters, and I don't know how to calculate the back ones, the following is only for reference The remaining volume: cubic centimeters; Cubic centimetre.

2. The end point? It should be the midpoint.

If it's the midpoint, you can do that.

Let the speed of car A be 3x and the speed of car B be 2x

3x+2x)*3 2+36=3*3xor (3x+2x)*3 2-36=3*2x

The solution is x=24

Distance between two places = (3 * 24 + 2 * 24) * 3 = 360 km.

Is the volume of the pencil after use? Is the long 6 an unused cylinder and the short 3 a used cone?

Cylindrical base area = 9 18 = square centimeters.

Volume = cubic centimeters.

2. The distance ratio of the two vehicles = the speed ratio of A and B in the same time = 3:2ab distance = (36 + 36) (3-2) (3 + 2) = 360 kilometers.

1. No picture, if not according to the considerations in life, theoretically, the original length is 18cm, and the current length is (6+3) cm, the length is reduced by half, and the volume is also reduced by half.

Second, if the question is the end, then you have to consider whether it is in A or B, it is a bit troublesome, you look at the question first, if it is the end, I will tell you again.

If it is the midpoint, then, from the question, the speed ratio of car A and B is 3:2, t = 3 hours, and the difference between s = 36km, so the difference between v = 36 3 = 12km h, that is, the speed of car A and B is 36 and 24km h.

The sum of the speed of A and B is 60km h, and the total number of s = 60 * 3 = 180km

What about the figure? Question 2:

Let A be 3x kmh and B 2xkmh.

There are two possibilities.

1）3x*3=36

x = 4 speed: A 12, B 8

Total length 62) 2x*3=36

x = 6 speed: A 18, B 12

Total length 90

First, the bottom area of the cylindrical pencil can be found: the height of the cylinder with the volume of the cylinder, and the column formula is as follows:

The volume is 3cm and 3cm respectively.

Second, the speed ratio of A and B is 3:2

180 km.