In this paper, an exact fuzzy modeling is adapted to design a nonlinear controller/observer for an inverted pendulum on a cart. Based on computed torque method, the nonlinear model is simplified, and two scalar valued auxiliary functions are defined and used to construct a full fuzzy model. Based on the obtained model, efficient and more practical controller and observer are designed with less complexity to stabilize the inverted pendulum on a cart. Simulation results are provided to illustrate the fruitfulness of the proposed methodology and the accuracy of the designed observer.