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A bag is filled with marbles. You take out and mark 80 marbles. Then you put the marbles back in the bag and mix the marbles. In a sample of 20 marbles, 4 of the marbles are marked. About how many marbles are in the bag?

A bag is filled with marbles You take out and mark 80 marbles Then you put the marbles back in the bag and mix the marbles In a sample of 20 marbles 4 of the ma class=