Sam buys 10 apples for $1. At what price should he sell a dozen apples if he wishes to make a profit of 25%?  Choices:
A) $0.125
B) $1.25
C) $0.25
D) $1.5
E) $1.8
Explanatory Answer   The cost price of 1 apple = $1/10 or $0.10.   As Sam wishes to make a profit of 25%, his selling price per apple should be 0.10 + 25% of 0.10 = 0.1 + 0.025 = $0.125.   If the selling price of 1 apple is $0.125, the selling price of a dozen apples = 12 * 0.125= 
<gadget id="calculator">12 * 0.125</gadget>
<output>1.5</output>
$1.5   Choice $1.5
<result>D</result>
Sam buys 10 apples for $1. At what price should he sell a dozen apples if he wishes to make a profit of 25%?