Tom's mathematics test had 60 questions: 10 arithmetic questions, 30 algebra questions and 20 geometry questions. Although he correctly answered 70% of the arithmetic questions, 40% of the algebra questions and 50% of the geometry questions, he did not pass the test because he got fewer than 60% of the questions right. How many more questions would he have needed to answer correctly to earn a passing grade of 60%?
10 • 70% = 7 correct
30 • 40% = 12 correct
20 • 50% = 10 correct
total 29 correct
60 • 60% = 36 to pass
36 – 29 = 7 Tom needed 7 more correct answers to pass
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