A teacher gave the same test to three history classes: A, B, and C. The average (arithmetic mean) scores for the three classes were 65, 85, and 77, respectively. The ratio of the numbers of students in each class who took the test was 4 to 6 to 5, respectively. What was the average score for the three classes combined? Options.
A) 74	B) 75	C) 76	D) 77	E) 78
ratio is 4:6:5 , numbers are 4x, 6x, 5x   total scores of each class is (65*4x + 6x * 85 + 77*5x) = 260x+510x+385x = 1155x   total number of students 260 +510 +385= 
<gadget id="calculator">260 +510 +385</gadget>
<output>1_155</output>
1155x   total number of students= 15x   average = 1155x/15x = 77   77 is the answer1155 /15= 
<gadget id="calculator">1155 /15</gadget>
<output>77</output>
77   77 is the answer
<result>D</result>
A teacher gave the same test to three history classes: A, B, and C. The average (arithmetic mean) scores for the three classes were 65, 85, and 77, respectively. The ratio of the numbers of students in each class who took the test was 4 to 6 to 5, respectively. What was the average score for the three classes combined?