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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?

Explanation	Calculations	Help
$We first create an unknown for the opening price using "At the opening of a trading day at a certain stock exchange, the price per share of stock K was 8 dollars" and let P_{open} be its value$	$P_{open} = 8$	Theory & Tactics Method Card TRANS1-A Click to view full details Theory & Tactics Method Card TRANS1-B Click to view full details
$We then create an unknown for the closing price using "the price per share of stock K was 9 dollars at the closing of the day" and let P_{close} be its value$	$P_{close} = 9$	Theory & Tactics Method Card TRANS1-A Click to view full details Theory & Tactics Method Card TRANS1-B Click to view full details
$We translate the concept of "percent increase" using the percent change formula$	$\frac{P _{close} - P _{open}}{P _{open}} \times 100%$	Theory & Tactics Method Card TRANS2-D Click to view full details
$We substitute the known values for P_{close} and P_{open}$	$\frac{9 - 8}{8} \times 100% = \frac{1}{8} \times 100%$
$We convert to a percent using the common fraction equivalency$	$12.5%$	Theory & Tactics Method Card FDPR1-A Click to view full details

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12.5%, which corresponds to answer choice D

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?

Explanation	Calculations	Help
$We first create an unknown for the opening price using "At the opening of a trading day at a certain stock exchange, the price per share of stock K was 8 dollars" and let P_{open} be its value$	$P_{open} = 8$	Theory & Tactics Method Card TRANS1-A Click to view full details Theory & Tactics Method Card TRANS1-B Click to view full details
$We then create an unknown for the closing price using "the price per share of stock K was 9 dollars at the closing of the day" and let P_{close} be its value$	$P_{close} = 9$	Theory & Tactics Method Card TRANS1-A Click to view full details Theory & Tactics Method Card TRANS1-B Click to view full details
$We translate the concept of "percent increase" using the percent change formula$	$\frac{P _{close} - P _{open}}{P _{open}} \times 100%$	Theory & Tactics Method Card TRANS2-D Click to view full details
$We substitute the known values for P_{close} and P_{open}$	$\frac{9 - 8}{8} \times 100% = \frac{1}{8} \times 100%$
$We convert to a percent using the common fraction equivalency$	$12.5%$	Theory & Tactics Method Card FDPR1-A Click to view full details

Scroll horizontally to view all columns

12.5%, which corresponds to answer choice D