Question

If you mixed 80 tons of sand, 12 tons of rock, and 4.0 tons of cement to make concrete, what would the percent by weight of sand be?

Answer 1

The percent by mass would be 83 %.

Explanation:

The mass percent of a component in a mixture is given by the formula

`color(blue)(|bar(ul(color(white)(a/a) "Mass Percent" = "Mass of component"/"Mass of mixture" × 100 % color(white)(a/a)|)))" "`

In your problem,

`"Mass of sand = 80 T"`
`"Mass of mixture" = "mass of sand + mass of rock + mass of cement" = "80 T + 12 T + 4 T" = "96 T"`

∴ `"Mass percent of sand" = ( 80 color(red)(cancel(color(black)("T"))))/(96 color(red)(cancel(color(black)("T")))) × 100 % = 83 %`