A teacher grades 100 papers in 5 hours. After coffee, her speed drops by 20%. If she grades for 3 more hours, how many papers in total?
Correct answer: B. 148
- A. 145
- B. 148
- C. 150
- D. 155
Explanation
Initially, the teacher grades 100 papers in 5 hours, giving a speed of 20 papers per hour. After coffee, her speed drops by 20%, reducing it to 16 papers per hour. Over the next 3 hours, she grades 48 papers (16 papers/hour * 3 hours). Adding this to the initial 100 papers results in a total of 148 papers graded. Option A (145) miscalculates the papers graded after the speed drop. Option C (150) ignores the reduction in speed and calculates based on the initial rate. Option D (155) significantly overestimates by not accounting for the speed decrease.
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