For the theatre the cost of a child ticket is `1/3` of the cost of an adult ticket. If the cost of tickets for `3` adults and `3` children is `Rs. 60`, the cost of an adult ticket is-

Options

A. Rs. 12
B. Rs. 15
C. Rs. 18
D. Rs. 20

Answer

To solve the problem, we need to find the cost of an adult ticket given the relationship between the cost of child and adult tickets and the total cost of tickets for 3 adults and 3 children.

### Step-by-Step Solution:

1. **Define Variables**:
Let the cost of an adult ticket be \( A \) (in Rs). According to the problem, the cost of a child ticket is \( \frac{1}{3} \) of the cost of an adult ticket. Therefore, we can express the cost of a child ticket as:
\[ C = \frac{1}{3} A \]

2. **Set Up the Equation**:
We know that the total cost for 3 adult tickets and 3 child tickets is Rs. 60. We can express this mathematically:
\[ 3A + 3C = 60 \]

3. **Substitute the Value of C**:
Substitute \( C \) from step 1 into the equation:
\[ 3A + 3\left(\frac{1}{3} A\right) = 60 \]

4. **Simplify the Equation**:
Simplifying the equation gives:
\[ 3A + A = 60 \]
\[ 4A = 60 \]

5. **Solve for A**:
To find the cost of an adult ticket, divide both sides by 4:
\[ A = \frac{60}{4} = 15 \]

6. **Conclusion**:
Therefore, the cost of an adult ticket is Rs. 15.

### Final Answer:
The cost of an adult ticket is Rs. 15.