Textbook Problem

Psychology Early in the twentieth century, an intelligence test called the Stanford-Binet Test (more commonly known as the IQ test) was developed. In this test, an individual’s mental age M is divided by the individual’s chronological age C and the quotient is multiplied by 100. The result is the individual’s IQ.

$IQ\left(M,C\right)=\frac{M}{C}\times 100$

Find the partial derivatives of IQ with respect to M and with respect to C. Evaluate the partial derivatives at the point (12, 10) and interpret the result. (Source: Adapted from Bernstein/Clark-Stewart/Roy/Wickens, Psychology, Fourth Edition)