Question

A teacher can grade 25 papers in 4 hours.

Answer 1

25/4= 6.25

6.25(6)=37.5

The teacher can grade 37.5 papers in 6 hours.

Answer 2

Well if she can grade 25 in 4 hours..
First we have to find out how many she can grade in 1 hour 
to find that out you can just divide the papers/hours= the paper per 1 hour 
25/4= 6.25 papers per hour 
So then to figure out how many papers the teacher can grade in 6 hours you multiply the number of papers per hour x the number of hours= number of papers in 6 hours 
6.25*6= 37.5 papers in 6 hours 
so the answer would be A) 37.5