Select the correct answerIn a class of 100 students, there are 70 boys whose average marks in a subject are 75. If the average marks of the complete class is 72, then what is the average marks of the girls?Options64687465
Question
Select the correct answerIn a class of 100 students, there are 70 boys whose average marks in a subject are 75. If the average marks of the complete class is 72, then what is the average marks of the girls?Options64687465
Solution
To solve this problem, we first need to find the total marks of the whole class and the total marks of the boys. Then we subtract the total marks of the boys from the total marks of the whole class to find the total marks of the girls. Finally, we divide the total marks of the girls by the number of girls to find the average marks of the girls.
Step 1: Find the total marks of the whole class. The average marks of the whole class is 72, and there are 100 students, so the total marks of the whole class is 72 * 100 = 7200.
Step 2: Find the total marks of the boys. The average marks of the boys is 75, and there are 70 boys, so the total marks of the boys is 75 * 70 = 5250.
Step 3: Find the total marks of the girls. The total marks of the girls is the total marks of the whole class minus the total marks of the boys, so the total marks of the girls is 7200 - 5250 = 1950.
Step 4: Find the average marks of the girls. The number of girls is the total number of students minus the number of boys, so there are 100 - 70 = 30 girls. The average marks of the girls is the total marks of the girls divided by the number of girls, so the average marks of the girls is 1950 / 30 = 65.
So, the correct answer is 65.
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