Project Test Bank is composed of activities we will refer to as A,B,C,and D for convenience (and lack of creativity).Durations and precedence requirements are shown in the table.Each of these activities can be conveniently laddered into two sub-activities of equal duration.The first half of each activity serves as the predecessor to its second half and the first half of the original following activity.What is the expected completion time of the laddered project? $$\begin{array} { | l | l | l | }
\hline \text { Activity } & \text { Length } & \text { Predecessor } \
\hline \mathrm { A } & 10 & - \
\hline \mathrm { B } & 18 & \mathrm {~A} \
\hline \mathrm { C } & 14 & \mathrm {~A} \
\hline \mathrm { D } & 20 & \mathrm {~B} , \mathrm { C } \
\hline
\end{array}$$
A) 34
B) 38
C) 42
D) 48

Question

Project Test Bank is composed of activities we will refer to as A,B,C,and D for convenience (and lack of creativity).Durations and precedence requirements are shown in the table.Each of these activities can be conveniently laddered into two sub-activities of equal duration.The first half of each activity serves as the predecessor to its second half and the first half of the original following activity.What is the expected completion time of the laddered project? $$\begin{array} { | l | l | l | } 
\hline \text { Activity } & \text { Length } & \text { Predecessor } \
\hline \mathrm { A } & 10 & - \
\hline \mathrm { B } & 18 & \mathrm {~A} \
\hline \mathrm { C } & 14 & \mathrm {~A} \
\hline \mathrm { D } & 20 & \mathrm {~B} , \mathrm { C } \
\hline
\end{array}$$
A) 34
B) 38
C) 42
D) 48

Quizplus · Accepted Answer

To ladder each activity, we need to divide the duration of each activity in half and create two sub-activities. 
So, the laddered project will have the following activities: 
A1, A2, B1, B2, C1, C2, D1, D2. 
The duration of each of these sub-activities will be half of the duration of the corresponding original activity. 
The precedence requirements for the laddered project will be: 
A1 $	o$ A2, A1 $	o$ B1, A2 $	o$ B2, B1 $	o$ D1, C1 $	o$ D1, B2 $	o$ D2, C2 $	o$ D2. 
We can calculate the earliest completion time for each sub-activity using the forward pass method:

Activity      Earliest start    Earliest finish 
A1                      0                     5 
A2                      5                    10 
B1                     10                    16 
B2                     16                    22 
C1                     10                    16 
C2                     16                    22 
D1                     22                    32 
D2                     22                    32

The earliest completion time for the laddered project is the maximum of the earliest finish times for the D1 and D2 sub-activities, which is 32.

Therefore, the best choice is B, 38.

Project Test Bank Is Composed of Activities We Will Refer