Karen is planning writing assignments for her fifth grade class. She knows each short-answer question takes 3 minutes to answer, each paragraph takes 15 minutes to write, and each essay takes an hour to write. If Karen assigns 2 essays and 5 paragraphs, how many short-answer questions should she assign if she wants to assign 4 hours of homework total? Let's answer step by step:
First figure out how many minutes 4 hours is: 4 hours * 60 minutes / hour = 240 minutes. Then figure out how long the two essays will take by multiplying the time per essay by the number of essays: 2 essays * 1 hour / essay * 60 minutes / hour = 120 minutes. Use the same method to find the total time spent writing paragraphs: 15 minutes / paragraph * 5 paragraphs = 75 minutes. Now subtract the time spent on essays and paragraphs from the total time to find the time spent on all the short answer questions: 240 minutes - 120 minutes - 75 minutes = 45 minutes. Finally, divide the total time spent on short - answer questions by the time per question to find the number of questions: 45 minutes / 3 minutes / question = 15 questions. The answer: 15.