Question

Two cubes of bronze have their total weight equivalent to $60$ kg. The first piece contains $10$ kg of pure zinc and the second piece contains $8$ kg of pure zinc. What is the percentage of zinc in the first piece of bronze if the second piece contains $15$ percent more zinc than the first?

• A. $15\%$
• B. $25\%$
• C. $55\%$
• D. $24\%$

Answer 1

Answer: (B)

$25\%$

Let first and second piece of bronze be = $xkg,(60-x)$kg
$\frac{8}{60-x}-\frac{10}{x}=\frac{15}{100}$

$\frac{8x-600+10x}{x(60-x)}=\frac{3}{20}$

$3x^2+180x-12000=0$
$x=40\%=\frac{10}{40}\times 100=25\%$