Posted by **iris** on Wednesday, October 26, 2011 at 11:38am.

john and mary are working on a job together. if john does it alone, it will take him seven days, while mary can do it alone in five days. how long will it take them to do it together?

- math -
**bobpursley**, Wednesday, October 26, 2011 at 11:44am
john rate= job/7hrs

mary rate=job/5 hrs

combined rate= job/7hrs+job/5hrs= (5+7)/35= 10/35 job/hr

so, time= howmuch/rate= 1job/(10jobs/35hrs)= 3.5 hrs

- math -
**Steve**, Wednesday, October 26, 2011 at 5:02pm
Or, if you use base 10, where 7+5=12, that would be 35/12 hours, or 2 hours 55 min

The 3.5 hours caught my eye, because that would be the time taken by 2 people who take 7 hours each.

## Answer This Question

## Related Questions

- math - 1.a collection of 105 coins consists of 1 peso and 5 pesos. if the total ...
- Algebra, URGENT!!! - 1) Mio can build a large shed in 15 days less than Yuuko ...
- Math(work problem) - A man can do the job in 8 days after 3 days of working a ...
- college algebra - the following rational function gives the number of days it ...
- basic algebra - Carlo,Clyde,and Marky working together can do a job in 6 days. ...
- Math - John can paint a room in 3 hours. His apprentice, working alone, requires...
- math - john takes 3hours longer than andrew to peel 400 pounds of apples. if ...
- college problem solving 2 - Me and Bill said casey can do the job for you in 10 ...
- intermediate Algebra - Mio can build a large shed in 7 days less then yuuko can...
- math - If A can do a job in 6 days that V can do in 5 1/2 days and C can do in 2...

More Related Questions