Rough Calculation for manpower requirement

Hi,

I am Pranav Patil, recently I have faced one interview. They asked me to calculate manpower required for a building RCC work whereas building has 4000 Sqm built up area for each floor. Total floors are 30 Nos. Scheduled completion is 15 Month.

I calculated manpower requirement as follows. Please suggest me if I wrong.

Total Nos. of floors -  30 Nos.

Completion time     -  15 Months

Cycle time to complete one floor  -  30/15 = 0.5 Months = 15 Days.

Carpenter Required 

Shuttering work quantum -  4000 x 1.5 = 6000 Sqm (Multiplied by 1.5 for shuttering for beams)

Days to ready slab shuttering = Cycle time / 2 =  15/2 = 7 Days

Per day productivity required = 6000/7 = 858 Sqm

Carpenter + Carpenter helper required = 858 /7 = 123 Nos.  (Productivity = 7 Sqm/day/(C+CH))

Barbender Required 

Concrete work qunatum = 4000 x0.15 = 600 Cum  (considered 0.15 thk of slab)

Quantum of reinforcement work = 600 x 0.1 = 60 MT

Per day productivity required  = 60/7 = 8.57 MT

Barbender + Barbender helper required = 8.57/0.15 = 57 Nos.

Total Manpower required:

Carpenter          = 123 Nos.

Carpenter helper = 123 Nos.

Bar bender         = 57  Nos.

Barbender Helper = 57 Nos.

Concreting helper  = 20 Nos.

Mason forfinishing = 2 Nos.

Total Manpower for RCC work = 382 Nos.

Please correct me if I wrong.