Question

You purchase a total of 45 shares of stocks from 3 different companies. You purchase twice as many shares of company c stock as you do company a. Company a stock sells for $15, company B sells for $12, and company C sells for $18. 
A) define a single variable and write an equation for the total cost of the stock
B) if you bought 10 shares of company A stock, what was the cost
C) Six months later the value of company A's stock increased 25%, and company C's decreased 10%. Write a new equation to express the value of the stock now. 
D) what is the percent of increase or decrease in the value of your purchase from part b?

Answer 1

A)The total cost would be: x=15a+12b+18c where x is the total cost and a,b,and c are the amount of stocks you bought from their respective companies.

B) Since you bought 10 A stocks, you must have bought 20 C stocks. That adds up to 30 bought, leaving 15 for B.

x=(15)(10)+(12)(15)+(18)(20)
x=150+180+360=$690 spent

C) A's stock is now 15(1.25) which is 18.75. C's stock is now 18(.90) which is 16.2
new equation is 18.75a+12b+16.2c=x

D) Substitute the number of stocks we bought from each in again:
187.5+180+324=$691.5

The cost went up slightly, so divide 690/691.5 then multiply that number by one hundred. You get that you spent in B 99.8% the amount you spent in C. So 100-99.8= an increase of .2%