A bowl contains 7 red balls and 10 blue balls. A woman selects 4 balls at random from the bowl. How many different selections are possible if at least 3 balls must be blue?

1050 possible selections

Explanation:

Number of red balls = 7

Number of blue balls = 10

Let blue balls be B and red balls be R

four balls are to be selected. At least three must be blue.

the first combination is 4blue 0red

second combination is 3blue 1red

(10C4*7C0 + 10C3*7C1)

210 * 1 + 120 * 7

210+840

=1050 possibilities