Let's roll up our sleeves and solve this. We have 251 and we're going to multiply it by 10, essentially adding 251 to itself 10 times.
Step 1: 0 + 251 = 251
Step 2: 251 + 251 = 502
Step 3: 502 + 251 = 753
Step 4: 753 + 251 = 1004
Step 5: 1004 + 251 = 1255
Step 6: 1255 + 251 = 1506
Step 7: 1506 + 251 = 1757
Step 8: 1757 + 251 = 2008
Step 9: 2008 + 251 = 2259
Step 10: 2259 + 251 = 2510

So, 251*10 = 2510