OK, let's crack this. We're given 378 and our task is to multiply it by 10. Essentially, we'll be adding 378 to itself 10 times.
Step 1: 0 + 378 = 378
Step 2: 378 + 378 = 756
Step 3: 756 + 378 = 1134
Step 4: 1134 + 378 = 1512
Step 5: 1512 + 378 = 1890
Step 6: 1890 + 378 = 2268
Step 7: 2268 + 378 = 2646
Step 8: 2646 + 378 = 3024
Step 9: 3024 + 378 = 3402
Step 10: 3402 + 378 = 3780

So, 378*10 = 3780