I have a spreadsheet like:

Lot   Slot Cars   Tagged Properly
A       1      2       1
B       1    10      10
A       2    5         4
B       2    1         1
C       3     3        2

I have about 400 rows of this type of data.  Basically I want to
generate some graphs showing the percent of cars properly tagged per
lot:

Lot   Properly Tagged
A      71%
B      100%
C      66%

What is the best way to do this?  I tried a pivot table and I can get
a sum of the cars per lot and a sum of the properly tagged cars in
that lot, but can't make it do a percentage.  Is there a formula I
could use for this OR would there be a better way to record this data
in the future?

Thanks,
 Andrew V. Romero