Calculating Percent Change

[njharper65]

Dear Tutor. Thank you for your assistance. I am in my mid fifties and returning to school. Some of my math skills I have let get rusty over the past 30 years. I appreciate your assistance. I am lost on this one. Don't even know where to start. I am trying to relearn all this again. A family member helped me; but, since they couldn't show me how they got the answer, it didn't help me. I need to understand what to do, so I know how to reach the answer, so I can apply what I learned to future mathematical equations.

Q. After several shares of the company's stock were sold, a profit of $1,320 was earned. The profit was 15% over a 30 day period. How much were the shares worth when they were purchased?

A. $198
B. $8,800
C. $1,122
D. $8,000

 

[Deleted member 4993]

Dear Tutor. Thank you for your assistance. I am in my mid fifties and returning to school. Some of my math skills I have let get rusty over the past 30 years. I appreciate your assistance. I am lost on this one. Don't even know where to start. I am trying to relearn all this again. A family member helped me; but, since they couldn't show me how they got the answer, it didn't help me. I need to understand what to do, so I know how to reach the answer, so I can apply what I learned to future mathematical equations.

Q. After several shares of the company's stock were sold, a profit of $1,320 was earned. The profit was 15% over a 30 day period. How much were the shares worth when they were purchased?

A. $198
B. $8,800
C. $1,122
D. $8,000

Okay then - let us define profit in this case:

Let:

Purchasing price = P

Selling price = S

\(\displaystyle profit (\text %) \ = \ \left (\frac{S}{P} - 1\right )\) * 100

Do you understand the equation written above?

 

[HallsofIvy]

I don't see that the "over a 30 day period" is at all relevant. If the original cost was "C" then "15% of the the cost" is 0.15*C= $1320. To get C by itself we need to "undo" that multiplication by 0.15, divide both sides by 0.15: C= (0.15*C)/0.15= 1320/0.15.

 

[jonah2.0]

Beer soaked ramblings follow.

Let me paint you a redundant landscape: C*1.15 - C = 1320

 

[njharper65]

Okay then - let us define profit in this case:

Let:

Purchasing price = P

Selling price = S

\(\displaystyle profit (\text %) \ = \ \left (\frac{S}{P} - 1\right )\) * 100

Do understand the equation written above?

Yes! Thank you for your assistance!!! Wishing you a lovely day.