Since Michaela needs 20 oranges to eat to her full, and Cassandra eats twice as much to have her full, Cassandra needs 2*20 = <<20*2=40>>40 oranges to eat.
They eat 20+40 = <<20+40=60>>60 oranges together to have their fill.
If they picked 90 oranges today, after eating 60 together, 90-60 = <<90-60=30>>30 oranges would remain.
#### 30