It takes Cynthia 11 hours to proof a chapter of Hawkes Learning Systems Intermediate Algebra book and it takes Mandy 5 hours. How long would it take them working together?

2 Answers
Oct 27, 2017

Together it would take 3 7/16 hours

Explanation:

Cynthia can proof (1" chapter")/(11" hours")=1/11 "chapters/hour"

Mandy can proof (1" chapter")/(5" hours")=1/5 "chapters/hour"

Together in one hour they could proof
1/11" chapters" +1/5" chapters"=(5+11)/55" chapters"=16/55" chapters"

16/55 " chapters"/" hour"=(1" chapter")/(55/16" hours")=(1" chapter")/(3 7/16" hours")

Oct 27, 2017

3 7/16 hours

Explanation:

Cynthia took 11 hours to proof a chapter. So, in 1 hour she proofs 1/11 th part of that chapter.

Mandy took 5 hours to proof that chapter. So, in 1 hour he proof 1/5 th part of that chapter.

So, in 1 hour they proof together = 1/11 + 1/5 = (5+11)/55 = 16/55 th parts.

Total time taken by them to complete proofs the chapter
rArr 1 -:16/55 = 1. 55/16 = 3 7/16hours.