OK, let's crack this. We're given 909 and our task is to multiply it by 10. Essentially, we'll be adding 909 to itself 10 times.
Step 1: 0 + 909 = 909
Step 2: 909 + 909 = 1818
Step 3: 1818 + 909 = 2727
Step 4: 2727 + 909 = 3636
Step 5: 3636 + 909 = 4545
Step 6: 4545 + 909 = 5454
Step 7: 5454 + 909 = 6363
Step 8: 6363 + 909 = 7272
Step 9: 7272 + 909 = 8181
Step 10: 8181 + 909 = 9090

So, 909*10 = 9090