On the oracle bones, ten was a single upright rod — a full bundle stood on its end — with a knot in the middle. The knot stretched into a crossbar, and 十 was born. With 一 to 十 you can build every number to ninety-nine: 三十 is three tens, 十三 is ten-three. No new words to memorize — just arithmetic you can read.
A piece of culture
The abacus: a computer of beads China has counted in tens for over three thousand years — the oracle bones already use a full decimal system, long before most of the world. Its greatest monument is the suanpan, the Chinese abacus: rows of beads on rods, ten per column. In trained hands it beat mechanical calculators well into the 20th century; shopkeepers' fingers flew over the beads for two thousand years. In 2013 UNESCO placed the abacus on the world heritage list of humanity.
Use it in a real word
十月
shíyuè · sap6 jyut6
October — "month ten"; you can now read every month of the year