Numbers with 1~9 (cannot be repeated)

There are four groups of solutions except192 384 576:192 384 576.

327 654 98 1

2 19 438 657

273 546 8 19 1. Xiao Zhao rides a motorcycle between A and B, with an average speed of 60 kilometers per hour. If you walk 55 kilometers per hour, you should return to location A on time. How many kilometers per hour did you average when you came back? Analysis: (1): We can regard the distance between A and B as the unit "L". According to time = distance/speed, we can know that the time to go is, the total round-trip time is 2/60 =, and the return time is-=. According to "distance ÷ time = speed", the average return speed can be calculated as 1÷( 1/66)=66 (km). (2) It can be assumed that the distance between A and B is 330 kilometers and the time to walk is 330÷55=6 (. The formula is 330 ÷ (330× 2+60—330 ÷ 55) = 66 (km) (3): Let the average journey per hour when returning be X km. According to the equality of the total round-trip time, the equation can be listed: so the average return time is 66 km/h. 2. The age difference between Party A and Party B (both over 10 year old) is 2 1 year old. Is it possible that in a certain year, the two figures of their age are just the opposite? Analysis: does not exist. Assuming that they exist, their ages are respectively, where >; The age difference is that it should be a multiple of 9, and 2 1 cannot be divisible by 9. 3. There are two triangles with areas of 6 and 8 in the trapezoid, and the length of the lower bottom of the trapezoid is twice as long as that of the upper bottom. Try to find the area of the shadow. Analysis: If the upper bottom is 3 and the lower bottom is 4, the height of the trapezoid is 4+4=8, the area of the trapezoid is (3+4)×8÷2=28, and the area of the blank part is 28–6–8 =14.4. (★★★★★★ Multiple-choice questions of Olympic Mathematical Network) A train and B train are hourly respectively. Car A leaves city A 1 hour earlier than car B, but arrives at city B at the same time. Find out the distance between the two cities. Analysis: (Method 1) Because Car A left first 100km, Car B can catch up with Car A every hour (120- 100)=20 (km), and it takes (100 ÷ 20) = The formula is (km). (Method 3) Time difference required for two cars to walk one kilometer each: (hours). Because the time difference between the two cars is 1 hour, the two cars should go separately = the car travels 40 kilometers per hour, which is 2.5 times the speed of the bicycle. As a result, grandpa arrived at B three hours earlier than Xiao Li. What's the distance between a and b? Analysis: (Method 1) According to "the speed of a car is 2.5 times that of a bicycle", at the same time, from place A to place B, it takes 2.5 times more time to ride a bicycle, that is, it takes 1.5 times more time than taking a car, and the corresponding specific amount is 3 hours, indicating that it takes 3 hours to take a car (2.5- 1) = 40.