I have two data frames df1 and df2 with three columns in each. I want to find the duplicate rows based on the first two columns and replace the third column of the duplicate entries in df1 with the sum of third columns in the corresponding duplicate entries

simple exsample

```
df1
col1 col2 col3
80.3    30.3    15
80.3    30.2    15
80.3    30.4    15
80.3    30      15
80.3    29.9    15
80.4    29.9    10

```

```
df2
col1 col2 col3
80.3    30.3    5
80.3    30.2    5
80.3    30.4    5
80.3    30      5
80.3    29.9    5

```

```
expected result
80.3    30.3    20
80.3    30.2    20
80.3    30.4    20
80.3    30      20
80.3    29.9    20
80.4    29.9    10

```

And how exactly i should introduce tolerance level of 0.01 in col1 and col2 for finding duplicates?