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?

A. 10%

B. 15%

C. 20%

D. 25%

E. 30%

C, 20%

Step-by-step explanation:

First we are told that she has 3 hours to grade 35 student papers, and she has 30 minutes to grade 5 paper, now we calculate how long it took her to grade 1 paper.

Part1

if 5papers = 30minutes

therefore 1paper = (30*1) / 5 = 6mins per paper.

now we are left with 2hrs 30mins (150 mins) to grade 30papers

Part2

if 30papers = 150minutes

therefore 1paper = (150*1) / 30 = 5mins per paper.

to calculate how fast she has to be in relation to the first part

we substract:

(6mins - 5mins) / 5mins * 100 = 1/5 * 100 = 20%.