Check my maths/logic please

AHarvey · 13 Apr 2008 at 13:15

Hello,

Right, I am trying to develop a system at work that monitors the amount of chairs that are being built in assembly.

Got a little spreadsheet that keeps track of certain things for me:

Pallet number - starts at 1 every day, used to record total number of finished pallets taken into the warehouse.

Time - Time the pallet was taken out.

Quantity of chairs on the pallet when it was taken out.

Type of chair - to monitor if some take longer to build than others

No. of staff - this number changes depending on other things.

What I need to do is work out how long a single chair takes to build in man minutes. For those that do not know, one man working for an hour = 1 man hour, 5 men working for one hour = 5 man hours.

I total up the number of chairs for the day, I average the number of staff for the day, I add the time taken all day in minutes minus 45 mins for breaks.

Now to work out how long it takes in man minutes to build one chair:

TOTAL TIME X AVERAGE No. OF STAFF = to get total man minutes for the day.

I then divide the total number of chairs built by the total man minutes.

Is that right?

Normally, these things I can do blindfolded but I must have had a brain fart during the night because this just doesn't look right.

Vonhelmet · 13 Apr 2008 at 13:18

Divide total number of chairs by total number of minutes to get the time taken to make one chair.

|Ric| · 13 Apr 2008 at 13:20

TOTAL TIME / AVERAGE No. OF STAFF = man minutes used that day

Ignore me

DaveF · 13 Apr 2008 at 13:26

AHarvey said:
Now to work out how long it takes in man minutes to build one chair:

TOTAL TIME X AVERAGE No. OF STAFF = to get total man minutes for the day.

I then divide the total number of chairs built by the total man minutes.

Is that right?

That looks right, yes. Only don't you know the actual number of staff? Because using an average there is probably going cause a lot of inaccuracy.

Amleto · 13 Apr 2008 at 13:58

as long as you know how to calculate the correctly-weighted average number of staff, then it's ok... as long as you want the average time in minutes for one chair. However, you said you wanted to be able to check for differences in times between different chairs.

AHarvey · 13 Apr 2008 at 14:12

DaveF said:
That looks right, yes. Only don't you know the actual number of staff? Because using an average there is probably going cause a lot of inaccuracy.

Yes, well we should have 7-8 staff permanetely working on chairs, however if we have loading or unloading they are stealing staff out of assembly to cover that. Firday for instance, I had just 3 members of staff in assembly.

Amleto said:
as long as you know how to calculate the correctly-weighted average number of staff, then it's ok... as long as you want the average time in minutes for one chair. However, you said you wanted to be able to check for differences in times between different chairs.

I just want to be able to see which chairs are taking longer to build than others. The main aim of the sheet is to calculate how many man minutes it takes to build one chair.

Zogger · 13 Apr 2008 at 14:14

vonhelmet said:
Divide total number of chairs by total number of minutes to get the time taken to make one chair.

that gives you chairs per minute... you want minutes per chair which is the other way round

Amleto · 13 Apr 2008 at 16:16

AHarvey said:
I just want to be able to see which chairs are taking longer to build than others. The main aim of the sheet is to calculate how many man minutes it takes to build one chair.

then one thing you need that wasn't mentioned explicitly: You need to be able to determine not only how many workers, but how many workers on a specific type of chair, and for how long.

PMKeates · 13 Apr 2008 at 16:30

Zogger said:
that gives you chairs per minute... you want minutes per chair which is the other way round

1 / chairs per minute