A number of studies on analogical transfer to algebra word problems have demonstrated that adapting a known solution to nonisomorphic problems of the same type is challenging, and that most instructional aids do not alleviate this difficulty. We designed a non-interactive intervention intended to encourage students to formulate situation models for base and target, and to ground their equations in these representations. One of our experimental groups had to simulate the situation models via manipulating physical objects. The other group had to perform internal simulations. Both conditions outperformed a control group not required to run simulations, yielding comparable advantage. Situation model elaboration proved more effective when targets posed more difficulty of equational assimilation. The implications of these findings for the design of instructional interventions are discussed.