The grade point average of one third of the classroom is 15; the grade point average of the rest is 18. What is the grade point average of the whole class?  Choose the correct choice.
A) 17 B) 19 C) 21 D) 23 E) 25
Let n=total students in class   total points for 1/3 class=15n/3=5n   total points for 2/3 class15 /3= 
<gadget id="calculator">15 /3</gadget>
<output>5</output>
5n   total points for 2/3 class=18*2n/3=12n   total points for whole class18*2 /3= 
<gadget id="calculator">18*2 /3</gadget>
<output>12</output>
12n   total points for whole class=5n+12n=17n   17n total class points/n total students5 +12= 
<gadget id="calculator">5 +12</gadget>
<output>17</output>
17n   17n total class points/n total students=17 grade point average for total class   17nswer : 17
<result>A</result>
The grade point average of one third of the classroom is 15; the grade point average of the rest is 18. What is the grade point average of the whole class?