GMAT Practice Question: At the opening of a trading day at a certain stock exchange, the price per share of stock K was...
Question
At the opening of a trading day at a certain stock exchange, the price per share of stock K was 8 dollars. If the price per share of stock K was 9 dollars at the closing of the day, what was the percent increase in the price per share of stock K for that day?
- 1.4 \%
- 5.9 \%
- 11.1 \%
- 12.5 \%
- 23.6 \%
Topics: word problems, percentages, translations
Solution
Step 1
We first create an unknown for the opening price using \textbf{"At the opening of a trading day at a certain stock exchange, the price per share of stock K was 8 dollars"} and let P_{\text{open}} be its value
P_{\text{open}} = 8
Step 2
We then create an unknown for the closing price using \textbf{"the price per share of stock K was 9 dollars at the closing of the day"} and let P_{\text{close}} be its value
P_{\text{close}} = 9
Step 3
We translate the concept of \textbf{"percent increase"} using the percent change formula
\dfrac{P_{\text{close}} - P_{\text{open}}}{P_{\text{open}}} \times 100\%
Step 4
We substitute the known values for P_{\text{close}} and P_{\text{open}}
\dfrac{9 - 8}{8} \times 100\% = \dfrac{1}{8} \times 100\%
Step 5
We convert \frac{1}{8} to a percent using the common fraction equivalency
12.5\%
Answer
12.5\%, which corresponds to answer choice D
