Answer: 1 hour for both parties to do this work. 1/5,
B, c, 1/4 hours to do this work,
"Party B works alone for 6 hours, and Party A and Party C cooperate for another 2 hours", which can be regarded as two parts: (1) Party A and Party C work for 2 hours and Party B for 4 hours; (2) B did it for another 2 hours.
(1/4+1/5) * 2 = 9/10, which means that A and C have worked for 2 hours and B has worked for 4 hours;
Then1-9/10 =110 was completed by Party B in 2 hours, so it takes 2/(110) = 20 hours for Party B to complete it alone.
Comprehensive formula: 2/[1-(1/4+1/5) * 2] = 20 hours.
2.A and B cars leave from AB station at the same time. Two hours and 24 minutes later, they met. When they met, car A was better than car B. 6 kilometers, it is known that it takes 4 hours and 30 minutes for a car to go from Station A to Mile Mile. What are the speeds of car A and car B respectively?
Answer: 2 hours and 24 minutes =2.4 hours, 4 hours and 30 minutes =4.5 hours; When Party A and Party B met, Party A experienced 2.4/4.5=8/ 15.
"Car A traveled 9.6 kilometers more than when car B met" means that car A exceeded the midpoint by 9.6/2=4.8 kilometers at this time.
So the whole journey is 4.8/(8/15-1/2) =144 km,
So the speed of A is144/4.5 = 32km/h; The speed of B is 9.6/2.4=4 km, and 32-4 = 28 km/h.
The comprehensive formula is: [(9.6/2)/(2.4/4.5-1/2)]/4.5 = 32km/h;
3. When the area of a circle is enlarged 16, how many times is the circumference enlarged?
Answer: The size of the circle is enlarged by 16 times, and 16=4*4, that is, the radius is enlarged by 4 times, so the circumference is also enlarged by 4 times.
Four students in a study group measured a cuboid.
Li Ming said: If the height is increased by centimeters, it is just a cube.
Wang Chen said: The sum of the areas of the front, back, left and right sides of a cuboid is 96 square centimeters.
Zhang Cheng said: Its bottom circumference is 24 cm.
All the data they said are correct. Find the volume of this cuboid.
Answer: there is a condition in the first sentence of this question that has not been typed, so I will take it as a,
"The height is increased by cm, which just happens to be a cube" means that this cuboid is now a special cuboid with a square top and bottom; "Its bottom circumference is 24 cm" means that the length and width of this cuboid are 24/4=6 cm.
"The sum of the front, back, left and right areas of a cuboid is 96 square centimeters." The front, back, left and right sides of this cuboid should be exactly the same rectangle, so the height of this cuboid is 96/4/6=4 cm.
So the volume of this cuboid is 6*6*4= 144 cubic centimeters.
6. In order to build a conservation-oriented society and strengthen citizens' awareness of water conservation, a city has formulated a water consumption charging standard: the monthly water consumption of each household does not exceed 10 cubic meter, and the tax per ton is 1.6 yuan. If it exceeds 10 cubic meter, the water fee will be increased by 50% on the basis of 1.6 yuan per cubic meter. The water fee for Mr. Li's family in April was 23.2. ~~~
Answer: 10* 1.6= 16 yuan,
23.2- 16=7.2 yuan
7.2/[1.6 * (1+50%)] = 3 cubic meters
3+ 10= 13 cubic meters.
The comprehensive formula is: (23.2-1.6 *10)/[1.6 * (1+50%)]+10 =13 m3.