Hello, thereddevils!

There are: . possible samples.Four bottles are filled with grade A sauce and three with grade B sauce.

If 3 bottles are randomly selected from the seven bottles,

what is the probability that both grades of sauces are in the selection?

There are two possible scenarios:

. . (1) Two A's and one B

. . . .

. . (2) One A and two B's

. . . .

Therefore: .

Someone else can show you the "complement" approach.

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