There are 11 boys and 13 girls in a class. If 1 boy is added to the class, what percentage of the class are girls?
There are a total of 11 + 1 = 
<gadget id="calculator">11+1</gadget>
<output>12</output>
12 boys in the class.
Hence, there are a total of 12 boys + 13 girls = 
<gadget id="calculator">12+13</gadget>
<output>25</output>
25 students in a class.
So 13/25 x 100% = 52% of the class are girls.

<result>52</result>