math
posted by borat .
Initially two painters are available to paint a picket fence. Peter alone could paint the fence in 6 hours; Pat alone in 3 hours. It is decided that they will work simultaneously to paint the fence. Before they start, however, along comes Mary, who alone could paint the fence in 8 hours.
Your task is to determine exactly how many minutes could be saved if all 3 painters work together on the fence, as compared to only Peter and Paul doing the job in tandem.
Determine how many additional minutes would be saved (beyond those found above) if Mary were able to paint the fence alone in 6 hours instead of 8 hours?

math 
Reiny
peter's rate = f/6
pat's rate = f/3
mary's rate = f/8
combided rate of all 3 = f/6 + f/3 + f/8
= 5f/8
time using all 3 = f/(5f/8) = 8/5 hrs or 1.6 hrs or
1 hour and 36 minutes
using only peter and paul = f/6 + f/3 = f/2
so time for the two of them is f/(f/2) = 2 hrs
so using Mary would save them 2 hrs  8/5 hrs or 24 minutes
You should have no difficulty repeating the calculations for the last part of the question.
Respond to this Question
Similar Questions

math
A man can paint a fence in 8 hours. Another man can paint that fence in only 7 hours. A third man can paint that fence in only 5 hours. How long will it take for all three men to paint the fence? 
Math
Al can paint a room in a hours working alone. Bill can paint a room in b hours working alone. Working alone, Bill takes tow more hours to paint a room than Al. Working together, they can paint a room in 8 hours. Write down a system … 
painting
Joe had eight sections of fence to paint. He painted 2/3 of each section in one hour. How many hours did it take him to paint all the section of the fence? 
Maths
Mr Jones takes 4 hours to paint a fence. Mark his son takes 6 hours to paint the same fence. How long does it take for them both to paint the fence? 
Intermediate Algebra
A painter can paint a fence in 12 hours working alone. His apprentice who works slower can paint the same fence in 24 hours. How many hours would it take to do the job if they worked together? 
Intermediate Algebra
A painter can paint a fence in 12 hours working alone. His apprentice who works slower can paint the same fence in 24 hours. How many hours would it take to do the job if they worked together? 
Algebra
mark can paint the fence in 40 minutes and manny can paint the fence in 30 minutes together how long will it take to paint the fence 
Math
when linda and martin work together painting one room, they can complete the work in 5 hours. when linda works alone it takes her 7 hours to paint the same room. how long would it take marvin to paint the room alone? 
Math
Sally can paint a fence in hour 30 minutes, but she calls Max to help and together they paint the fence in hour. How long would Max take if he were to paint the fence alone? 
math
Lexie is painting her fence. each foot of the fence requires 3/5 of a gallon of paint. Her fence is 8 3/4 feet long.what is the total amount of paint,in gallons Lexie needs to paint her fence?