You can put this solution on YOUR website! Points earned / possible points * 100 = percentage score.
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87.5/120 * 100 = 72.916666666%
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That rounds to 73%.
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But the grade depends on what the grading system says it is. There is no standard for grades. Some schools use 7-point ranges, some use 10. Some use + and - grades, some don't. And so forth.
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Done