What is the mass in kg of a person who weighs 185 pounds?

##185 lb~~84.2 kg##
This question can be answered by using dimensional analysis.
The relationship between kilograms and pounds is ##1 kg=2.20 lb##.
This gives us two conversation factors:
##1 kg/2.20 lb## and ##2.20 lb/1 kg##
Multiply the given dimension ##(185 lb)## by the conversion factor with the desired unit in the numerator. This will cancel the unit we wish to convert.
##185 lbxx(1 kg)/(2.20 lb)=84.2 kg## rounded to three significant figures.