A box contains 50 coloured balls, What is the total number of white balls in the box if the probability of selecting an white ball is 0 . 4 ?

Options

A. 20
B. 15
C. 10
D. 40

Answer

To solve the problem, we need to find the total number of white balls in a box containing 50 colored balls, given that the probability of selecting a white ball is 0.4.

### Step-by-Step Solution:

1. **Understand the Given Information**:
- Total number of balls in the box = 50
- Probability of selecting a white ball (P(White)) = 0.4

2. **Use the Formula for Probability**:
The probability of an event is given by the formula:
\[ P(E) = \frac{\text{Number of favorable outcomes}}{\text{Total number of outcomes}} \]
Here, the favorable outcome is selecting a white ball.

3. **Set Up the Equation**:
Let the number of white balls be \( x \). According to the probability formula:
\[ P(\text{White}) = \frac{x}{50} \]
We know that \( P(\text{White}) = 0.4 \). Therefore, we can set up the equation:
\[ \frac{x}{50} = 0.4 \]

4. **Solve for \( x \)**:
To find \( x \), multiply both sides of the equation by 50:
\[ x = 0.4 \times 50 \]
Now, calculate \( 0.4 \times 50 \):
\[ x = 20 \]

5. **Conclusion**:
The total number of white balls in the box is 20.

### Final Answer:
The total number of white balls in the box is **20**.

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