A bag contains 8 red balls, 10 blue balls, 17 green balls. What is the minimum number of balls that needs to be taken out from the bag to ensure getting at least one ball of each colour?
28
Bag Ball Problem: Finding the Minimum Number
This question asks for the minimum number of balls we need to draw from a bag to guarantee that we have at least one ball of each color.
The bag contains balls of three different colors:
- Red balls: 8
- Blue balls: 10
- Green balls: 17
To ensure getting at least one ball of each color, we must consider the worst-case scenario. The worst-case scenario is when we draw balls such that we delay getting one color as much as possible. This happens if we draw all the balls of the two most numerous colors before drawing any ball of the third color.
Let's identify the number of balls for each color:
- Red: 8
- Blue: 10
- Green: 17
The two largest groups of balls are Green (17 balls) and Blue (10 balls).
In the worst-case scenario, we would first draw all the Green balls, and then all the Blue balls.
Number of balls drawn in the worst case before getting the third color:
- All Green balls = 17
- All Blue balls = 10
Total balls drawn in the worst case so far = $17 + 10 = 27$.
After drawing 27 balls, according to the worst-case scenario, we have drawn all the Green balls and all the Blue balls. The only balls remaining in the bag are the Red balls.
Now, if we draw just one more ball, it must be a Red ball, because that is the only color left. Drawing this 28th ball guarantees that we have drawn at least one ball of each color (all 17 Green, all 10 Blue, and now 1 Red).
Therefore, the minimum number of balls that needs to be taken out from the bag to ensure getting at least one ball of each color is the sum of the counts of the two largest groups plus one.
Minimum number of balls = (Number of Green balls) + (Number of Blue balls) + 1
Minimum number of balls = $17 + 10 + 1 = 28$.
Drawing 28 balls guarantees that you have picked at least one red, one blue, and one green ball.
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