On Monday he picks 100 oranges.
On Tuesday, they pick thrice as much, which will be 3*100 = <<3*100=300>>300 oranges.
The total number of oranges picked now is 300+100 = <<300+100=400>>400 oranges.
On Wednesday, he adds 70 more, which will now be 400+70 = <<470=470>>470 oranges
#### 470