Abstract: A reversible arithmetic teaching device. In one embodiment, the device comprises a receptacle having on both sides a horizontal row of numbers with a corresponding arithmetic function below which is a window through which a reference number and arithmetically corresponding answers are visible. A slidable card is inserted in the receptacle. The card has on its first side a vertical column of numbers and an array of rows of comprising corresponding numerical answers. One number at a time on each vertical column is displayed through the window. Indicating means permit the indication of a selected arithmetic relationship between any one number in the column of numbers located at one end of the slidable card and any one of the horizontal row of numbers on the receptacle such that, upon applying the arithmetic designation with respect to the two cooperating numbers, a corresponding answer is displayed through the window.

Abstract: A composition for improving the heat reflectivity and the heat resistance of a metal substrate. The coating composition comprises a latex resin including acrylic polymers; silica; and a fire retardant including at least one of a phosphated pentaerythritol ammonium salt, an organo-polyphosphate ammonium salt, an ammonium salt, and a Magnesium salt. The silica reflects and resists heat. Additionally, the silica raises the decomposition temperature of the resin by insulating the resin from heat and reflecting heat away from the resin. This, in turn, increases the ability of the composition to maintain its bond to the substrate at high temperatures. As such, the coating remains on the substrate where it reflects and resists heat, i.e., it does not easily brush or rub off after several hours of exposure to high heat. The silica can be rice hull silica.