Question 389537
You want to end up with less than 25% lead, so
Let {{{x}}} = pounds of mixture to be added
In words:
(pounds of lead in final mixture)/(total pounds of mixture) = 25%
{{{(.15x + .45*2200)/(x + 2200) = .25}}}
{{{.15x + 990 = .25*(x + 2200)}}}
{{{.15x + 990 = .25x + 550}}}
{{{.1x = 440}}}
{{{x = 4400}}}
You must add more than 4400 pounds of mixture
To check, I'll add 4401 pounds
{{{(.15*4401 + .45*2200)/(4401 + 2200) < .25}}}
{{{(660.15 + 990)/6601 < .25}}}
{{{1650.15/6601 < .25}}}
{{{.249985 < .25}}}
looks right