2. The correspondent sent a letter from A to B, and immediately returned to A. * * * It took 3 hours and 52 minutes, with a speed of 30 km/h when he left and 28 km/h when he came back, to find the distance between A and B.
3.A walks 5 kilometers every hour, and after 2 hours, B rides a bike to chase A. ..
(1) If the speed of B is 20km/h, how long will it take for B to catch up with A?
(2) If B is required to go 14km to catch up with A, what is the speed of B?
4. Party A and Party B practice race walking on the 400-meter circular runway. Party B walks 80 meters per minute, and Party A's speed is 1 and1/4 (1/4). Now Party A is in front of Party B 100 meters. How many minutes did they meet for the first time?
1. has a three-digit number, and its unit is three times smaller than the number on the 100th place, and the number on the unit is 1. If you exchange the number in the tenth place and the number in the hundredth place of this three-digit number to get a new number, then the original three-digit number is 270 times smaller than the new number and the original three-digit number is found.
2. The school has a four-story teaching building with six classrooms on each floor and three doors (two front doors and one side door of the same size) entering and leaving the building. The door was inspected during the safety inspection; When a main entrance and a side door are opened at the same time, 400 students can pass through in 2 minutes. If the main entrance has an average of 40 more students per minute than the side entrance.
(1) How many students can pass through a main entrance and a side door every minute on average?
(2) During the inspection, it was found that the efficiency of going out was reduced by 20% because students were too crowded in an emergency. According to the safety regulations, in case of emergency, students in the whole building should be evacuated safely through these three doors within 5 minutes. Suppose that each classroom in this teaching building has a maximum of 45 students. Q: Do these three doors meet the safety requirements? Why?
3. Party A and Party B walk from City A to City B. Party A walks 4 kilometers per hour, while Party B rides 8 kilometers per hour more than Party A. After half an hour, Party B sets out and both of them arrive at City B at the same time to find the distance between the two cities.
4. Several students in Education Middle School asked for cancellation. If there are 4 people living in each dormitory, there are 20 people left; If there are 8 people living in each dormitory, one dormitory is not empty and the others are full. Q: How many dormitories are there in this middle school? How many students are required to live on campus?
1.(2x) cube * y cube divided by (16xy square)
2.(-a squared b) divided by (-1/2ab squared)
3.(- 1/5a cubic x quartic -9/ 10a square x cubic) divided by (-3/5ax square)
4.(-2π r squared h+3π rh squared) divided by (1/2π rh)
5+2 1*8/2-6-59
68/2 1-8- 1 1*8+6 1
-2/9-7/9-56
4.6-(-3/4+ 1.6-4-3/4)
1/2+3+5/6-7/ 12
[2/3-4- 1/4*(-0.4)]/ 1/3+2
22+(-4)+(-2)+4*3
-2*8-8* 1/2+8/ 1/8
(2/3+ 1/2)/(- 1/ 12)*(- 12)
(-28)/(-6+4)+(- 1)
2/(-2)+0/7-(-8)*(-2)
( 1/4-5/6+ 1/3+2/3)/ 1/2
18-6/(-3)*(-2)
(5+3/8*8/30/(-2)-3
(-84)/2*(-3)/(-6)
1/2*(-4/ 15)/2/3
- 1+2-3+4-5+6-7
-50-28+(-24)-(-22)
- 19.8-(-20.3)-(+20.2)- 10.8
0.25- +(- 1 )-(+3 )
- 1-〔 1-( 1-0.6÷3)〕×〔2-(-3)×(-4)〕
0÷(-4)-42-(-8)÷(- 1)3
-32-(-3) 2-(-3)3+(- 1)6
3×(-2)2+(-2×3)2+(-2+3)2
(- 12)÷4×(-6)÷2
(- 12)÷4×(-6)×2
75÷〔 138÷( 100-54)〕
85×(95- 1440÷24)
80400-(4300+870÷ 15)
240×78÷( 154- 1 15)
1437×27+27×563
〔75-( 12+ 18)〕÷ 15
2 160÷〔(83-79)× 18〕
280+840÷24×5
325÷ 13×(266-250)
85×(95- 1440÷24)
58870÷( 105+20×2)
1437×27+27×563
8 1432÷( 13×52+78)
[37.85-(7.85+6.4)] ×30
156×[( 17.7-7.2)÷3]
(947-599)+76×64
36×(9 13-276÷23)
-(3.4 1.25×2.4)
0.8×〔 15.5-(3.2 1 5.79)〕
(3 1.8 3.2×4)÷5
194-64.8÷ 1.8×0.9 36.72÷4.25×9.9
3.4 16÷(0.0 16×35)
0.8×[( 10-6.76)÷ 1.2]
( 136+64)×(65-345÷23)
(6.8-6.8×0.55)÷8.5
0. 12× 4.8÷0. 12×4.8
(58+37)÷(64-9×5)
8 12-700÷(9+3 1× 1 1)
(3.2× 1.5+2.5)÷ 1.6
85+ 14×( 14+208÷26)
120-36×4÷ 18+35
(284+ 16)×(5 12-8208÷ 18)
9.72× 1.6- 18.305÷7
4/7÷[ 1/3×(3/5-3/ 10)]
(4/5+ 1/4)÷7/3+7/ 10
12.78-0÷( 13.4+ 156.6 )
37.8 12-700÷(9+3 1× 1 1)
( 136+64)×(65-345÷23)
3.2×( 1.5+2.5)÷ 1.6
85+ 14×( 14+208÷26)
(58+37)÷(64-9×5)
(6.8-6.8×0.55)÷8.5
(284+ 16)×(5 12-8208÷ 18)
0. 12× 4.8÷0. 12×4.8
(3.2× 1.5+2.5)÷ 1.6
120-36×4÷ 18+35
10. 15- 10.75×0.4-5.7
5.8×(3.87-0. 13)
+4.2×3.74 347+45×2-4 160÷52
32.52-(6+9.728÷3.2)×2.5 87(58+37)÷(64-9×5)
[(7. 1-5.6)×0.9- 1. 15] ÷2.5 (3.2× 1.5+2.5)÷ 1.6
5.4÷[2.6×(3.7-2.9)+0.62] 12×6÷( 12-7.2)-6
3.2×6+( 1.5+2.5)÷ 1.6 (3.2× 1.5+2.5)÷ 1.6
5.8×(3.87-0. 13)+4.2×3.74