A bowl contains 10 red balls and 10 blue balls. A womanselects balls at random without looking at them.A) how many balls must she select to be sure of havingat least three balls of the same color?B) how many balls must she select to be sure of havingat least three blue balls?
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A) After 1st and 2nd pick up, she won't have 3 of the same color for sure.
After the third pickup, she may have (2,1) (each number in the bracket stands for the number of balls for a given color).
After the fourth pickup, she may have (2,2)
After the fifth pickup, she may have (5,0), (4,1) or (3,2). In all cases, she will always have 3 of the same color.
Therefore, at least 5 pickups.
B) Worst case scenario is for her to pick the 10 red balls first. So she needs to have at least 13 pickups.
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