Peter, Bob and Jack do a work. If they work in pairs: Peter and Bob can complete it in 12 hours; Bob and Jack can complete it in 10 hours; Jack and Peter can complete it in 15 hours. Peter needs ........ hours to complete this work by himself.
Peter, Bob and Jack do a work. If they work in pairs: Peter and Bob can complete it in 12 hours; Bob and Jack can complete it in 10 hours; Jack and Peter can complete it in 15 hours. Peter needs ........ hours to complete this work by himself.
Peter, Bob and Jack do a work. If they work in pairs: Peter and Bob can complete it in 12 hours; Bob and Jack can complete it in 10 hours; Jack and Peter can complete it in 15 hours. Peter needs ........ hours to complete this work by himself.
a. 18b. 40c. 24c. 421.Peter, Bob and Jack do a work. If they work in pairs: Peter and Bob can complete it in 12 hours; Bob and Jack can complete it in 10 hours; Jack and Peter can complete it in 15 hours. Peter needs ........ hours to complete this work by himself.
2.The product of 2 natural numbers is 2015. Find the smallest possible sum of these two numbers?
Answer: The smallest possible sum of these numbers is ...............
Peter,Bob and Jack do a work.If they work in pairs:Peter and Bob can complete if in 12 hours;Bob and Jack can complete it in10 hours;Jack and Peter can complete it in 15 hours.Peter need hours to complete this work by himself.
Trong 1 giờ Peter + Bod = 1/12 ( CV )
Bod + Jack = 1/10 ( CV )
Jack + Peter = 1/15 ( CV )
Ta thấy mỗi bạn đều xuất hiện 2 lần nên trong 1 giờ cà 3 bạn làm được là:
( 1/12 + 1/10 + 1/15 ) : 2 = 1/8 ( CV )
Peter làm được số phần của công việc là:
1/8 - 1/10 = 1/40 ( CV )
Peter làm công việc đó hết số giờ là:
1 : 1/40 = 40 ( giờ )
Đáp số : 40 giờ
Peter, Bod và Jack làm một công việc. Họ làm việc theo cặp. Peter và Bod có thể làm xong công việc này trong 12 giờ, Bod và Jack có thể làm xong công việc trong 10 giờ, Jack và Peter có thể làm xong công việc trong 15 giờ. Hỏi một mình Peter có thể làm xong công việc trong b/n giờ ?
Peter, Bob and Jack do a work. If they work in pairs: Peter and Bob can complete it in 12 hours; Bob and Jack can complete it in 10 hours; Jack and Peter can complete it in 15 hours. Peter needs ........ hours to complete this work by himself.
a. 18b. 40c. 24c. 42Peter, Bob và Jack cùng làm một công việc. Nếu họ làm theo cặp: Peter và Bob có thể hoàn thành nó trong vòng 12 giờ; Bob và Jack có thể hoàn thành trong 10 giờ; Jack và Peter có thể hoàn thành trong 15 giờ. Peter cần ......... giờ để một mình hoàn thành công việc này.
Nếu cả 3 bạn cùng làm thì 1 giờ làm được là :
(1/12+1/10+1/15):2=1/8(công việc)
Nếu một minh peter làm thì 1 giờ làm được là:
1/8-1/10=1/40(công việc)
1 giờ làm được 1/40 công việc vậy 40 giờ peter sẽ làm xong công việc
There are 3 children in a family,Jack,Mary and Peter.Mary can clean the house for 1 hour.Jack can do thesame job for 2 hours and Peter needs 6 hours.If theydo the job together then they need ................ minutes.
If they do the job together then they need :
1 + 2 + 6 = 9 (hours)
= 540 minutes
k me
If they do the job together then they need
1+2+6=9 ( hours )
9 hours = 540 minutes
k me
Bob buy three times as many apples as Peter . Mia buys 7 apples more than Bob and 19 apples more than Peter. How many apples do they buy together ?
Ai biết giải thì hộ nhé
Peter,Bob và Jack làm 1 công việc.Nếu họ làm việc theo cặp:Peter và Bob có thể hoàn thành nó trong 12 giờ;Bob va Jack có thể hoàn thành nó trong 10 giờ;Jack và Peter có thể hoàn thành nó trong 15 giờ.Hỏi Peter cần bao nhiêu giờ để hoàn thành công việc này một mình
A robot cannot think or do things alone. People use a computer to control it. Today, robots are becoming useful in our lives. They can help us to save a lot of time and work. A robot can do the same work for 24 hours, and yet, it does not complain or get tired. In the US, people use robots as security guards in some important places. These robots can listen for certain noises and send signals for help if there’s trouble or danger. In Japan, people use robots in factories to build cars. In the future, scientists will design many types of intelligent robots. Their robots will help us to do many more complicated things. However, some people do not like robots. They fear that one day robots will be too powerful.
1. Why do people use a computer to control a robot?
A. Because it is very useful. B. Because it is too expensive.
C. Because it cannot think or do things alone. D. Because it can save time and work.
2. Which of the following statements is NOT TRUE according to the text?
A. People use computers to control robots. B. Robots do not get tired of working.
C. Robots cannot do the same work for 24 hours.
D. People use robots as security guards in some important places in the US.
3. The word “it” in the text refers to.
A. a robot B. work C. the US D. a computer
4. In Japan, people use robots in factories to_______.
A. do many more complicated things B. build cars
C. guard important places D. listen to certain noises
5. Some people fear that one day robots _______.
A. will have too much power B. will do complicated things
C. will be busier than humans D. will make too much noise