Which inequality is true?

Helpp due now

The multiplication property of zero states that the product of any number and 0 is 0. what must be true about either a or b to make ab=0

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

Aresearch study is done to find the average age of all u. s. factory workers. the researchers asked every factory worker in ohio what their birth year is. this research is an example of a census survey convenience sample simple random sample