Answer
1kg of nickels is 200 nickels.
Work Step by Step
Use ratio and cross multiplication to find the number of nickels. Remember that the ratios must use the same unit of measure. 1kg is 1000g.
$\frac{1\ nickel}{5\ g}=\frac{x\ nickels}{1000g}$
$5x=(1)(1000)$
$5x\div5=1000\div5$
$x=200$