Answer
$44\ ft^3$ sand
Work Step by Step
Create a proportion using ratios of sand:concrete.
$\frac{2.75\ ft^3\ sand}{8\ ft^3\ concrete}=\frac{x\ ft^3\ sand}{128\ ft^3\ concrete}$
Set the product of the means equal to the product of the extremes and solve for the variable.
$8 \times x=2.75\times 128$
$8x=352$
$8x\div8=352\div8$
$x=44$
