Combined scale used to solve the equations and the following inequalities:

摘要

879,088. Educational appliances. ORLOV, K. Oct. 12, 1959 [Oct. 14, 1958], No. 34467/59. Class 146(2). An educational aid for demonstrating mathematical operations comprises three balances a, b, c, the beam 8 of the centre one being connected with the beams 2, 19 of the other two balances so as to compare the unbalance between the scale pans of the other two balances, one scale pan of each balance e.g. 1 20 representing positive quantities and the other e.g. 6, 22 negative quantities. A pointer 9 attached to the beam 8 carries a bar 10 and when this is parallel to a fixed bar 11 then one side = the other but if bar 10 is tilted the two bars make either of the two mathematical signs or .