Question

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?

Answer 1

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")`

Answer 2

`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 7/16`hours.