PLEASE HELP ASAP start off by restating: Historians know about the past before there were written records by studying artifacts The three main types of artifacts are physical, visual, and oral traditions.

step-by-step explanation:

and 90% of people marry there 7th grade love. since u have read this, u will be told good news 2night. if u don't pass this on nine comments ur worst week starts now this isn't fake. apparently if u copy and paste this on ten comments in the next ten minutes you will have the best day of ur life tomorrow. you will either get kissed or asked out in the next 53 minutes someone will say i love u

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ending amount = beginning amount / (2^n)

where "n" = number of half-lives (or elapsed time / half-life)

ending amount = 50 mg / (2 ^10 / 5.3)

ending amount = 50 mg / (2 ^ 1.8867924528)

ending amount = 50 m / 3.6981210597

ending amount = 13.5203794557 mg

or about 13.5 mg remain

source:  

the answer for this is 0.25 km. : )