Rate of change: If y = f(x), then dy/dx gives the rate of change of y with respect to x. If x and y are both functions of time t, then dy/dt = f'(x) * dx/dt (chain rule for related rates).

Common related rates problems:

1. Expanding circle: dA/dt = 2pir * dr/dt
2. Filling cone: V = $\frac{1}{3}$pi$r^2$*h, with r/h = constant
3. Ladder sliding: $x^2$ + $y^2$ = $L^2$, differentiate with respect to t
4. Shadow problems: similar triangles + chain rule

JEE approach:

1. Draw a diagram
2. Identify all variables and given rates
3. Find an equation relating the variables
4. Differentiate with respect to t
5. Substitute known values and solve for unknown rate

Example: A balloon's radius increases at 2 cm/s. Find the rate of volume increase when r = 5 cm. V = $\frac{4}{3}$pi$r^3$. dV/dt = 4pi$r^2$ * dr/dt = 4pi252 = 200pi $cm^3$/s.