Which product is great than 3/4?

News cameras take an overhead picture of a crowd at an outdoor event journalist then count the total number of people in the picture and use the sample of estimate the total number of people in the crowd this process is an example of

Jonathan can type 20 documents in 40 minutes ,and susan can type it in 30 minutes and jack can type it in 24 minutes working together ,how much time will it is take them type the same document

Julie was able to walk 16 km through the zoo in 6 hours. how long will it take her to walk 24 km through the zoo?