The Number Test of the ACER Mathematics Profile Series, contains 30 items, for each of three suggested grade levels: 7-8, 8-9, and 9-10. Raw scores on all tests in the ACER Mathematics Profile Series (Number, Operations, Space and Measurement) are converted to a common scale called MAPS, a major feature of the Series. Based on the Rasch Model, MAPS makes it possible to estimate the likelihood of a student with a known ability being able to correctly answer an item of known difficulty. Broadly speaking, MAPS also makes it possible to measure the latent variable underlying the Series: mathematics development. Expected mastery levels for test items are related to four Piagetian developmental stages: early concrete operational; late concrete operational; early formal operational; and late formal operational. The objectives which are suggested are process, rather than content, oriented. Based loosely upon Bloom's Taxonomy, they relate mathematics development to such cognitive processes as knowledge, operations, classification, ordination, relevance, creativity, and problem solving. (CP)