How much does a social worker make? According to the May 2012 records from the Bureau of Labor Statistics, the mean annual healthcare social worker salary is $51,460, or $24.74 per hour. The lowest ten percent earn $31,410, while the top ten percent make an average of $74,030 annually.
The Leibniz Step Reckoner. Gottfried Leibnizâs 1673 âStep Reckonerâ introduced a design innovation that enabled a single gear to represent any digit from 0 to 9 in just one revolution. This stepped-drum approach dominated calculator design for the next two centuries. Gottfried Leibniz.
Models made before the end of the 19th century are very rare and are usually only to be seen in museums and books. These include the Pascaline invented by Blaise Pascal, and the Stepped Reckoner invented by Leibniz, both in the 17th century, and Charles Xavier Thomas's Arithmometer in the 19th century.