This paper presents the teaching of mathematics in a volatile, uncertain, complex and ambiguous world with the use of concrete-representational-abstract instructional strategy (CRAIS). The CRAIS involves active participation of students in learning. The study adopted the pretest-posttest, control group, quasi experimental design. 191 senior secondary II students from four public schools purposively selected from two local government areas in Ibadan municipality were randomly grouped into one experimental and one control group. The experimental group was exposed to CRAIS and the control to modified conventional teaching strategy for 6 weeks. Instrument used was Students' Mathematics Achievement Test (r = 0.83). Two instructional guides on CRAIS and modified conventional teaching strategy were also used. Data were subjected to analysis of covariance. It was found out that the performance of the students taught with CRAIS improved significantly. Therefore, the teachers of mathematics should learn the use of CRAIS for effective teaching of mathematics.