A sporting goods store ordered an equal number of white and yellow tennis balls. The tennis ball company delivered 30 extra white balls, making the ratio of white balls to yellow balls 6.5. How many tennis balls did the store originally order?

Options

A. `120`
B. `150`
C. `240`
D. `300`

Explanation

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

1. **Understanding the Problem**: The store ordered an equal number of white and yellow tennis balls. We need to find out how many tennis balls were originally ordered.

2. **Setting Up the Variables**: Let the number of white balls (which is equal to the number of yellow balls) be represented by \( y \).

3. **Adjusting for Extra Balls**: The company delivered 30 extra white balls. Therefore, the total number of white balls becomes \( y + 30 \).

4. **Setting Up the Ratio**: According to the problem, the ratio of white balls to yellow balls is given as \( 6:5 \). This can be expressed mathematically as:
\[ \frac{y + 30}{y} = \frac{6}{5} \]

5. **Cross Multiplying**: To eliminate the fraction, we can cross-multiply:
\[ 5(y + 30) = 6y \]

6. **Expanding the Equation**: Distributing the 5 on the left side gives:
\[ 5y + 150 = 6y \]

7. **Rearranging the Equation**: To isolate \( y \), we can subtract \( 5y \) from both sides:
\[ 150 = 6y - 5y \]
This simplifies to:
\[ 150 = y \]

8. **Conclusion**: Since \( y \) represents the number of white (and yellow) balls originally ordered, the store originally ordered 150 tennis balls of each color.

9. **Final Answer**: Therefore, the total number of tennis balls originally ordered is:
\[ 150 + 150 = 300 \]