Question

Complete 20km=------m

Answer 1

`\sf 1~kilometer = 1,000 ~meters\\\\20~km= 20 * 1000~m=\boxed {\sf20,000~m}`

Answer 2

"kilo" means a thousand in Greek, so one kilo-meter is literately a thousand meters. (some people i know write "k" in slang for a thousand).

so 20 km is 20 thousand meters, which is 20 000 m.