Potassium Content of Tomatoes. The size of the tomato you eat influences how much potassium you'll get from the vegetable. One large tomato contains 431 milligrams of potassium, which is almost 10 percent of your daily requirement. One medium-sized tomato supplies 292 milligrams of potassium and a small tomato provides 216 milligrams. A plum tomato or an Italian tomato each contains 147 milligrams of potassium.
The abacus, called Suan-Pan in Chinese, as it appears today, was first chronicled circa 1200 C.E. in China. The device was made of wood with metal re-inforcements. On each rod, the classic Chinese abacus has 2 beads on the upper deck and 5 on the lower deck; such an abacus is also referred to as a 2/5 abacus.
Chinese Abacus Project. People in China began to use an abacus to help them with math problems maybe as early as 500 BC. Nobody knows whether somebody in China invented the abacus, or whether they learned about it from people in the Persian Empire (modern Iran), who started using the abacus about the same time.