A laboratory mixture of $200\text{ g}$ contains dry sand and iron filings. If $40\%$ of the total mass of…
A laboratory mixture of $200\text{ g}$ contains dry sand and iron filings. If $40\%$ of the total mass of the mixture is iron filings, what mass of sand remains after all the iron filings are completely extracted using a strong magnet?
$80\text{ g}$
$120\text{ g}$
$140\text{ g}$
$160\text{ g}$
Solution
The mass of iron filings is $40\%$ of $200\text{ g} = 80\text{ g}$. Subtracting this from the total gives $200\text{ g} - 80\text{ g} = 120\text{ g}$ of remaining sand.