A comprehensive problem of geometry plus algebra in the third year of junior high school Given that the four sides of a convex quadrilateral ABCD are a, B, C, D in order, and AA + AB AC BC = 0, BB + BC BD CD = 0, then the quadrilateral ABCD is () A. Parallelogram B. rectangle C. diamond D. trapezoid

A comprehensive problem of geometry plus algebra in the third year of junior high school Given that the four sides of a convex quadrilateral ABCD are a, B, C, D in order, and AA + AB AC BC = 0, BB + BC BD CD = 0, then the quadrilateral ABCD is () A. Parallelogram B. rectangle C. diamond D. trapezoid

AA + AB AC BC = 0 deduces (A-C) * (a + b) = 0, a + B cannot be 0, so a = C
BB + BC BD CD = 0 (B-D) * (B + C) = 0
So a parallelogram

20 division problems, please,

136÷17
184÷23
325÷13
584÷73
814÷37
832÷64
945÷21
901÷53
833÷49
444÷12
851÷23
756÷21
864÷32
837÷31
767÷59
798÷14
731÷43
663÷17

From the two places to the opposite place at the same time, it takes 5 hours for a to complete the whole journey, and it takes 8 hours for B to complete the whole journey. When two people meet, how many parts of the whole journey does a take?

1 ÷（1/5 + 1/8）
= 1÷ 13/40
=40 / 13 hours meeting time
1/5 × 40/13 = 8/13
A walked 8 / 13 of the whole journey

I'm right about 2 / 5 / 3 / 7 x 8 / 9 = 2 / 5 x 7 / 3 / 9 / 8, but the answer is wrong. What's wrong?

Your operation is theoretically correct, but when we calculate such numbers, we convert division into multiplication, not multiplication into division. It's unnecessary to convert x 8 / 9 into △ 9 / 8

Mathematical Olympiad problems of fractional division
Six out of seven of () is three out of five kilometers
There is a fraction, the numerator plus 1 can be reduced to 1 / 4, the denominator minus 1 can be reduced to 1 / 5, this fraction is ()
There are three kinds of milk powder, which are 15 / 4 kg, 21 / 5 kg and 9 / 2 kg in weight. Now they need to be put into small bags without surplus, and they all have the same weight. How many bottles should they hold at least?
Third question, please explain the reason!

35 / 18 km
three-sixteenths
To minimize the number of bags, 3 / 20 kg per small bag, a total of 83 bags

Quick, about fractional division!
1. Five seventh of the number a is equal to seven twelfth of the number B, and the number a is (). If the number B is 84, the number a is ()
2. There are 51 white rabbits in the farm, accounting for three fifths of the total number of rabbits
A. The number of black rabbits B. the total number of rabbits C. cannot be determined
3. After one fifth of a wire is cut off, the remaining part is compared with four fifths of a meter, ()
A. The rest is as long as B. C. can't be compared
The speed of a truck is 80 kilometers per hour, the speed of a truck is four fifths of that of a car, and the speed of a car is how many kilometers per hour? Don't use the equation!
The distance between city a and city B is 180 kilometers. A car from city a to city B has driven five eighths of the whole journey. How many kilometers has this car driven?

1. Five seventh of the number a is equal to seven twelfth of the number B. the number a is (49 / 60 of the number b). If the number B is 84, the number a is (68.6)
5A / 7 = 7b / 12
A = 49 B / 60, where B is 84
A = 49 / 60 × 84
A = 68.6
2. There are 51 white rabbits in the farm, accounting for three fifths of the total number of rabbits
B. Total number of rabbits
Because 3 rabbits / 5 = 51
So the total number of rabbits = 51 △ 3 / 5
3. After one fifth of a wire is cut off, the rest is compared with four fifths of a meter
C. Can't compare
Because the length of the wire is uncertain, it cannot be compared,
4. The speed of a truck is 80 kilometers per hour, the speed of a truck is four fifths of that of a car, and the speed of a car is how many kilometers per hour? Don't use the equation!
What's the speed of the car
80÷4/5
=100 km / h
5. The distance between city a and city B is 180 kilometers. A car from city a to city B has driven five eighths of the whole journey. How many kilometers has this car driven?
The car has run
180×5/8
=112.5 km

About fractional division!
1. Five seventh of the number a is equal to seven twelfth of the number B, and the number a is (). If the number B is 84, the number a is ()
2. There are 51 white rabbits in the farm, accounting for three fifths of the total number of rabbits
A. The number of black rabbits B. the total number of rabbits C. cannot be determined
3. After one fifth of a wire is cut off, the remaining part is compared with four fifths of a meter, ()
A. The rest is long B. the total number of rabbits C. can't be compared
The speed of a truck is 80 kilometers per hour, the speed of a truck is four fifths of that of a car, and the speed of a car is how many kilometers per hour? Don't use the equation!
The distance between city a and city B is 180 km. A car from city a to city B has driven five eighths of the whole journey. How many kilometers has this car driven? Don't use the equation!
The third question is wrong,
3. After one fifth of a wire is cut off, the remaining part is compared with four fifths of a meter, ()
A. The rest is as long as B. C. can't be compared

1 49 / 60 B 343 / 5
2 B
3 C
80 / (4 / 5) = 100 km
180 * (5 / 8) = 112.5km

In December 2008, Li Zhuang's family owned a family car, which consumed 2000 liters of 93 gasoline a year. The country began to levy the fuel tax, and the oil price has been lowered. According to the price tag of 93 gasoline below, please calculate how much fuel money Li Zhuang's car can save a year compared with the original one after the fuel tax? {the original price of 93 gasoline is 5.97 yuan per liter, and the current price is reduced by 15.4%}

5.97 × 15.4% × 2000 = 1838.76 yuan

In a class, boys accounted for 3 / 5 of girls, and then there were 3 boys and 2 girls. At this time, boys accounted for 2 / 3 of girls. How many people are there in the class now?

Find the score equal to 3 / 5, see which molecule add 3, denominator add 2, just can be reduced to 2 / 3 (special find denominator add 2 can become a multiple of 3, and the molecule is just a multiple of 3) 6 / 10 No, that's 15 / 25, just become 18 / 27 = 2 / 318 + 27 = 45 people, there is a way to directly calculate, but too difficult to understand, see

Calculate by Division
When the clothing store bought 100 sets of children's clothing, the price of each set was 200 yuan. The boss expected to make a profit of 50%. When he sold 60% of the children's clothing, he sold out the rest of the children's clothing at a discount. As a result, the profit was 18% less than expected?

Actual income = 200 * 100 * (1 + 50% - 20%) = 26400 yuan
Front income = 200 * 100 * 60% * (1 + 50%) = 18000 yuan
Income after price reduction = 26400-18000 = 8400 yuan
Price reduction unit price = 8400 / 100 * (1-60%) = 210 yuan
Discount = 210 / 200 * (1 + 50%) = 0.7
Children's clothes sold at a discount of 70%