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There are 9 workers in a community and 6 of them will be selected to be interviewed.How many combinations?
A container leaks 27% of the water in the first hour and leaks 23% of the remainder in the second hour.What percentage of the water that was leaked during the first two hours?
7 green balls and 5 red balls,seclet 3 balls randomly,what is the possibility of choosing 3 red ones?
