Answer
a) 62.5 lb
b) 3 bags
Work Step by Step
a) Create a proportion using ratios of lb : square foot.
$\frac{25\ lb}{1200\ ft^2}=\frac{x\ lb}{3000\ ft^2}$
Set the product of the means equal to the product of the extremes and solve for the variable.
$1200\times x = 25\times3000$
$1200x=75000$
$1200x\div1200=75000\div1200$
$x=62.5$
b) Create a proportion using ratios of lb : bag.
$\frac{25\ lb}{1\ bag}=\frac{62.5\ lb}{x\ bag}$
Set the product of the means equal to the product of the extremes and solve for the variable.
$1\times 62.5 = 25\times x$
$62.5=25x$
$62.5\div25=25\div25$
$2.5=x$
Round up to 3 bags to have enough.
