Question 163788
</pre><font size=4><b>
Remember:
x=amount of 90% platinum
y=amount of 70% platinum
So, {{{x+y=3oz}}} --------------------> eqn 1
We get in eqn 1,
{{{y=3-x}}} --------------------------> eqn 2
Also,
{{{0.90x+0.70y=3oz(0.76)}}} ----------> eqn 3
Susbt eqn 2 in eqn 3:
{{{0.90x+0.70(3-x)=2.28}}}
{{{0.90x+2.10-0.70x=2.28}}}
{{{0.20x=2.28-2.10=0.18}}}
{{{cross(0.20)x/cross(0.20)=cross(0.18)0.90/cross(0.20)}}}
{{{x=0.90oz}}}, for 90%
Via eqn 2:
{{{y=3-0.90=2.10oz}}}, for 70%
Check via eqn 3,
{{{0.90(0.90)+0.70(2.10)=3(0.76)}}}
{{{0.81+1.47=2.28}}}
{{{2.28=2.28}}}
Thank you,
Jojo</pre>