review packet solutions to #11 and #23

11) In order to put the second equation in the desired format (in terms of one variable) you pick a variable to solve for in the first equation. I chose y. I took the equation 4x^2*y=100 and reaarranged it to y=100/4x^2. I then substituted this into the second equation for y and simplified. The unsimplified version is z=40x^2+20*x*100/4x^2. When you simplify this you get z=40x^2+500/x.

23)For this problem I used the form a*b^x. a=7 (starting amount) b=1/2 and x= 4.8/3.6 (this is the amount of time you have divided by the amount it takes for one half life to occur). Therefore, the overall equation is 7*(1/2)^(4.8/3.6) and this results with 2.78g left.