Question

A teacher has 3 hours to grade all the papers submitted by the 35 students in her class. She gets through the first 5 papers in 30 minutes. How much faster does she have to work to grade the remaining papers in the allotted time? Will it be wrong if I say '' she has to be 1.2 times faster instead of 20% faster?''

Answer 1

Let us calculate the teacher's initial speed. It can be calculated as thus:

She does 5 papers in 30 minutes. Thus means her speed is 6 minutes per paper (Because $\frac{30}{5}=6$ minutes per paper).

Now, if the teacher has to complete the remaining 30 papers in the remaining 150 minutes (2 hours 30 minutes=120+30=150 minutes), she will have to go through one paper in $\frac{150}{30}=5$ minutes. Thus, her speed now will have to be 5 minutes per paper.

Now, we know that 1.2 times 5=6. Therefore, it will not be wrong to say that '' she has to be 1.2 times faster instead of 20% faster" because both mean the same.