Dissection of a Parallelogram into Triangles, Ross Surface Form #10

This is the tenth in a series of models of plane figures (surface forms) designed by William Wallace Ross, a school superintendent and mathematics teacher in Fremont, Ohio. The unpainted wooden rhomboid (parallelogram) is bisected along a diagonal into two scalene triangles. Two adjacent sides on the left are equal, as are two adjacent sides on the right. A paper label attached to the model reads: Rhomboid B 4x6 Bisected. According to Ross, the model shows that if a rhomboid is cut diagonally through the obtuse angles, two equal scalene triangles result.
Compare models 1985.0112.190 through 1985.0112.202. For further information about Ross models, including references, see 1985.0112.191.
Currently not on view
Object Name
geometric model
date made
ca 1895
Ross, W. W.
Physical Description
wood (overall material)
overall: 1 cm x 17.2 cm x 10 cm; 13/32 in x 6 25/32 in x 3 15/16 in
place made
United States: Ohio, Fremont
ID Number
catalog number
accession number
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Arithmetic Teaching
Data Source
National Museum of American History, Kenneth E. Behring Center


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