Benny is a client with mental retardation. If his mental age is 10 and his chronological age is 20, what would be his intelligence quotient?

To determine Benny's intelligence quotient (IQ), we can use the formula:

[ \text{IQ} = \left( \frac{\text{Mental Age}}{\text{Chronological Age}} \right) \times 100 ]

In this case, Benny's mental age is 10 and his chronological age is 20. Plugging these values into the formula:

[ \text{IQ} = \left( \frac{10}{20} \right) \times 100 ]

This simplifies to:

[ \text{IQ} = 0.5 \times 100 = 50 ]

Thus, Benny's IQ is 50, which aligns with the choice given. Understanding the calculation of IQ this way is crucial, as it reflects how age and developmental abilities are compared to determine cognitive functioning in individuals with varying levels of mental ability. This method highlights both the mental and chronological aspects, emphasizing the delay or developmental disability in a structured numerical form.