Pick a ball

Topic: Logic

Difficulty: 3/10

Hint in 3…..

2………

1………

If you are really lucky, the answer would be 4. But in this case, think of the worst case scenario

Solution in 3…..

2………

1………

FULL SOLUTION

The keywords here are “certain” & “minimum”

Step 1: Worst case scenario: After taking out 8 balls, 3R, 2G & 3B

Step 2:The next ball must either be red or blue since there  are only 2 green balls.

Step 3: So 9 is the minimum number of balls needed.