The pattern behind the list
Every answer in the 30 times table ends in 0, so the list is easy to check: the answers are the 3 times table with a zero on the end.
Working out big facts
You do not need to learn all 20 facts by heart. Use the method for the 30 times table instead: 30 is 3 tens, so work out the 3s answer and write a zero on the end.
Work out 3 × 20 = 60, then add a zero: 600.
30 × 20 = 60 × 10 = 600