What number can be added to the numerator and denominator of 3 / 17 at the same time to get 3 / 5! What's the formula

What number can be added to the numerator and denominator of 3 / 17 at the same time to get 3 / 5! What's the formula

eighteen

Why divide a fraction by its reciprocal?
Such as the title

Because the reciprocal is 1 divided by the number, the original formula is a number * 1 divided by a number, that is, multiplied by the reciprocal of the number

Dividing by a number is equal to multiplying by the reciprocal of the number______ ．

Divide by a non-zero number is equal to multiply by the reciprocal of the number, the question lacks the restriction of divisor, wrong. So the answer is: wrong

The fifth grade application question 20 (must have the answer) anxious~~~~~~

[the division sign is replaced by #, and the multiplication sign is replaced by X
1: There are 90 ping-pong balls in sporting goods. If every two are packed in a box, can they be just finished? If every five are packed in a box, can they be just finished? Why?
90 × 2 = 45 boxes
90 × 5 = 18 boxes
A: if you pack one box for every two, you can just finish. If you pack one box for every five, you can just finish. Because 90 can divide five
2: There are 57 balls in the sports shop, three of which are packed in one box. Can they be just finished?
57 × 3 + 19 boxes
A: it's just finished
3: A and B type a 10000 word document. A type 115 words per minute, B type 135 words per minute. How many minutes can they finish?
10000 # (115 + 135) = 40 points
A: 40 minutes
4: Fifth grade students planting trees, 13 or 14 people in a group are just finished, fifth grade students to participate in planting trees at least how many people?
13x14 = 192
A: there are at least 192 people participating in tree planting in the fifth grade
Although the following questions belong to practical problems, they are related to equations. I use equations to solve them
5: Two cars travel from one place to the other. One car travels 31 kilometers per hour, the other 44 kilometers per hour. After how many minutes, the two cars are 300 kilometers apart?
Equation:
The two cars met after X
31X+44X=300
75X=300
X=4
4 hours = 240 minutes
A: after 240 minutes, the two cars are 300 kilometers apart
6: The two engineering teams have to dig through a 119 meter long tunnel together, and the two teams will work separately from both ends. Team a digs 4 meters every day, and team B digs 3 meters every day. How many days can we dig through the tunnel?
Tunnel excavation after X days
3X+4X=119
7X=119
X=17
A: it took 17 days to dig through the tunnel
7: There are 140 students in the school chorus and dance team. The number of students in the chorus is six times that of the dance team. How many students are there in the dance team?
Set up a dance team with X people
6X+X=140
7X=140
X = 20
A: the dance team has 20 people
It's not an equation problem from here on
8: The two brothers went to the gymnasium from home at the same time. The road was 1300 meters long. The elder brother walked 80 meters per minute. The younger brother rode a bicycle to the gymnasium at the speed of 180 meters per minute and returned immediately. On the way, he met his elder brother. How many minutes did the elder brother walk?
1300x2 = 2600m 2600m (180 + 80)
=2600#260
=10 points
A: at this time, my brother walked for 10 minutes
9:: on June 1, children's day, Miss Wang bought 360 biscuits, 480 pieces of candy and 400 fruits, making exquisite small gift bags, giving children as gifts. At most, how many small bags can be made?
360 + 480 + 400 = 1240
A: 1240 small gift bags at most
10: Mischievous bought 40 balloons and invited students to come home to compare and blow balloons. In order to divide the balloons equally, how many students should mischievous invite to compare and blow balloons? Mischievous does not participate
40 × 2 = 20, 40 × 4 = 10, 40 × 5 = 8
40 × 8 = 5 people 40 × 0 = 4 people 40 × 20 = 2 people
A: there are six ways to invite students: 20, 10, 5, 8, 4 and 2
11: A trapezoidal corn field, 15 meters above the bottom, 24 meters below the bottom, and 18 meters high. There are 9 corn plants per square meter on average. How many corn plants can be planted in this field?
(15 + 24) x18 × 2 = 351 M2
351x9 = 3195 strains
A: 3159 corn plants can be planted on this land
12: The number of students in a class is less than 100. When they line up, there are five, four and three more students in each row. How many students are there in this class?
5x4x3 = 60 people 60 + 1 = 61 people
A: there are 61 people in this class
13: Wang Yue has a box of chocolates, 7, 5 and 3 at a time. How many chocolates does this box have at least?
7x5x3 = 105 grains 105 + 1 = 106 grains
A: there are at least 106 chocolates in this box
14: Chenguang community has a 15 meter long, 1.2 meter wide rectangular corridor to be paved with square bricks. The designer has prepared 30 cm long square bricks, please calculate: how many such square bricks do you need? If each square brick costs 3 yuan, how much does it cost to pave this corridor?
15 m = 150 decimeters 1.2 m = 12 decimeters 30 cm = 3 decimeters
150x12 = 1800 square decimeters 3x3 = 9 square decimeters
1800 × 9 = 200 yuan, 200x3 = 600 yuan
Answer: need 200 such square brick, need 600 yuan
15: There are two parallelogram experimental fields of equal area. One is 70 meters long and 45 meters high at the bottom, and the other is 90 meters long and how high is it?
70x45 = 3150 square meters 3150 × 90 = 35 meters
A: the height is 35 meters
16: A batch of steel pipes are stacked in a pile. There are 10 steel pipes at the bottom layer, one less for each upper layer, and five steel pipes at the top layer. How many steel pipes are there in this batch?
10-5 + 1 = 6 floors (10 + 5) X6 × 2
=15X6#2
=90#2
=45
A: there are 45 steel pipes in this batch

How does the lever change the size and direction of the force? How does the pulley catch the direction of the edge force? How does it save effort

The lever can change the downward force to the upward force. The force can be changed by changing the torque
Pulley is also a kind of lever. Moving pulley can save labor

Why does the pulley just change the direction of the force and not the magnitude of the force?

The pulley is divided into fixed pulley and movable pulley
Fixed pulley can change the direction of force, but it can't save labor
-- your question has its own problems

On the problems of junior high school physics
It means that if the number of segments of the rope is odd, the driven pulley will wind the rope from the inside out in turn
If there is only one ordinary movable pulley, the center of the rope is hung with a heavy weight of 400N. Why is its pull force 200N? Because the odd and even are fixed. Conversely, the number of segments of a movable pulley should be odd and three segments. But how can the number of segments of an ordinary movable pulley be only two?

First of all, if you ask this question, it means that you use your brain to ponder over this law. Learning physics should be like this: only by understanding knowledge can you apply physics well! The so-called "odd and even determination" is for pulley block, which is used to judge whether the pulley block uses a piece of rope to hang goods

Junior high school physics pulley!
I --- I --- I --- I --- I --- ceiling
I I I I I
I I ○--------○I I○------○I
I I I I I
I'm connected to a big turntable
○ ○
------------------------------Clothes and clothes rack
Title: as shown in the figure, it is a schematic diagram of a hand lifting clothes hanger, which is composed of four fixed pulleys and two moving pulleys. The end of the rope is wound on a rotating wheel fixed on the wall, and the rotating handle can make the clothes hanger lifting. It is assumed that the cross beam of the clothes hanger remains horizontal during the lifting process. Q: suppose that the total weight of the clothes and the clothes hanger (including the moving pulley) is 50N, How much is the tension of the rope when it is still? The answer is 12.5 why? I wrote 10 mistakes! Experts ask!
I can't do it in the exam. The meaning of the title should be clear

There are four sections of rope around the movable pulley
F=50N/4=12.5N

As shown in Fig. 3-3-15, force F to lift the pulley up at a constant speed. If the weight g = 20n and follow the pulley up 1m at a constant speed, the correct statement about the size of F and the height h of the pulley up is (the weight and friction of the pulley are ignored)
A.F=20N h=1M
B.F=40N,h=2M
C.F=40N,h=0.5M
D.F=10N h=2M
The answer is C. I think we should choose D. what should we choose? Why
As shown in Fig. 3-3-17, apply a vertical downward pull on the hook of the moving pulley to make the object G rise at a constant speed
A. The force F is only half of G. B. the force F is equal to g
C. When the movable pulley hook moves down H / 2, the object G moves up for 2 h
D. When the object G moves up h, the moving pulley moves down H / 2
I don't know why?
The picture has not been reflected = =... How to do

1. If the weight and friction of the pulley are neglected, f = G + G '/ N (G is the weight of the object suspended under the pulley,
G 'is the weight of the pulley, n is the number of segments of the rope, and F is the tension at the free end of the rope
I guess the rope in your question should be two (perspiration), which is brought into the formula
0 is OK) calculate f = 10N
Another formula is s = NH (s is the rising height of the rope, and H is the rising height of the object)
You just bring in the formula
(PS: you seem to have made a mistake in "follow the pulley up 1m at a constant speed" and "pulley up height H"
It seems to mean the same thing
2 a wrong. (when the pulley weight and friction are not timing is half)
B wrong
C is wrong
D yes. (same reason)

Junior high school physics --- how to count the number of pulley rope segments?

If you can draw a picture, it will be clear at a glance
But I can also describe: when counting the number of pulley rope segments, the fixed pulley does not need to count, because it is not labor-saving and has nothing to do with calculation. So just count the moving pulley. As for how to count, in a word, just look at how many segments of the rope connected with the moving pulley (only those connected with the fixed pulley but not with the moving pulley), and how many are there