A bag contains 20 balls . These are of three different colours : green red and blue .A ball is chosen at random from the bag . The probability of a green ball is `(1)/(4)`. The probability of a red ball is `(2)/(5)` .
How many balls are green ?

Answer

To solve the problem step by step, we can follow these instructions:

### Step 1: Understand the total number of balls
We know that the total number of balls in the bag is 20.

### Step 2: Use the probability of green balls
The probability of selecting a green ball from the bag is given as \( \frac{1}{4} \).

### Step 3: Calculate the number of green balls
To find the number of green balls, we can use the formula for probability:

\[ P(\text{Green}) = \frac{\text{Number of Green Balls}}{\text{Total Number of Balls}} \]

From the problem, we have:

\[ \frac{\text{Number of Green Balls}}{20} = \frac{1}{4} \]

### Step 4: Set up the equation
Let \( x \) be the number of green balls. We can set up the equation:

\[ \frac{x}{20} = \frac{1}{4} \]

### Step 5: Solve for \( x \)
To solve for \( x \), we can cross-multiply:

\[ x \cdot 4 = 20 \cdot 1 \]

This simplifies to:

\[ 4x = 20 \]

Now, divide both sides by 4:

\[ x = \frac{20}{4} = 5 \]

### Step 6: Conclusion
Therefore, the number of green balls in the bag is \( 5 \).

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