Question

A teacher grades 25 students essays in 4 hours. Assuming he grades at the same speed, how long will it take him to grade 35 essays?
What is the constant of this variation?

Answer 1

For this case, the first thing we must do is define a variable:
 x: number of hours
 y: number of trials
 We write the equation that represents the problem:
 y = (25/4) x
 For 35 essays we have:
 35 = (25/4) x
 Clearing x:
 x = 5.6 hours
 Answer:
 it will take him to grade 35 essays about: 
 x = 5.6 hours
 the constant of this variation is:
 25/4 essays / hour