SOLUTION: In a large class, 80 students took a test. When the test papers were graded, it was founf that 10% of the students had A's. 25% of the students had B papers 30% of the students had

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Question 13175: In a large class, 80 students took a test. When the test papers were graded, it was founf that 10% of the students had A's. 25% of the students had B papers 30% of the students had C papers 15% of the students had D papers, and the rest failed the test. How many students failed the test?
Answer by akmb1215(68) About Me  (Show Source):
You can put this solution on YOUR website!
You know that the entire class is 100%, because 100% is the whole thing. So, figure out what percents you know already (10% had A's, 25% had B's, 30% had C's, and 15% had D's). Add those percentages up to see what you know (10+25+30+15 = 80%). You know now that 20% of the class failed the test.
Now you need to figure out what 20% of 80 is. We are doing 20% of 80 because there are 80 people in the class. To solve this, change 20% to a decimal (.20) and multiply by 80 (we are multiplying because "of" means to multiply in math). So, your equation looks like: .20%2A80+=+16. So, 16 people failed the test.