Blog Archive

Saturday, July 28, 2012

LAG AND LEAD QUESTION




Question: You are in the process developing a project schedule for repainting your house. In order to repaint your house, you first need to scrape off the existing paint, and then add a layer of primer. The primer provides the paint a better
bonding surface so it sticks to the base material much better. Without priming, drywall surfaces will soak up more finish paint in some areas than in others, producing a splotchy effect.
You decided to speed up the process by starting priming before all the scraping is finished. However, once the primer is applied, you must wait until the primer dries before adding on the actual paint. You estimate that it will take 8 hours for the primer to dry. To correctly sequence these activities, which of the following should you do?


(A) Add a lead time to the priming task with respect to scraping, and a lag time to the priming task with respect to
painting
(B) Add a lead time to the priming task with respect to scraping, and a lead time to the priming task with respect
to painting
(C) Add a lag time to the priming task with respect to scraping, and a lead time to the priming task with respect to
painting
(D) Add a lag time to the priming task with respect to scraping, and a lag time to the priming task with respect to
painting
----------------------------


Q: Activity A has a finish - to-finish relationship with activity B. Activity A has a
duration of 10 days. Activity B has duration of 9 days with a 3 day lag. what is the total
duration of activity a and B?
1.  7 days
2.  8 days
3.  12 days
4.  9 days
Correct answer would be 13 days.
FF+3
In above case
Bigger one Duration +LAG 
Total duration of A and B activities = 10+3
 In this case 
Suppose project starts by 6th of March 
We will demonstrate it
by Zero start method like this
9
18
B/9

(Start of project by 6th March) 5
FF+3
15

A/10


Project is finishing on 18.
Thus 6th March morning to 18th March evening = 18-5 = 13 days
 -------------------------
Question
 What is total duration of A and B activities?
B/11

FF-2

A/10

Suppose project finishes on 15th March.
By question - activity A will finish 2 days later than B. because activity B is taking 2days lead.
By zero start method we can illustrate it like this:
Here activity B has to start 1st
2
13
B/11

FF-2
5
15

A/10

By this presentation it is clear that project has to be started by activity B on 3rd of March to get finish on
March 15th.
Thus duration of project will be = 3rd to 15th = 15-2 = 13 days.
 What is total duration of below activities?
B/11

FF-2

A/10

Solution
Zero start method
5
16
B/11

FF-2
4
14

A/10



16-4=12 days


No comments:

Post a Comment