OK, let's work through this together. We're starting with 680 and we're going to multiply it by 16, which means we add 680 to itself 16 times.
Step 1: 0 + 680 = 680
Step 2: 680 + 680 = 1360
Step 3: 1360 + 680 = 2040
Step 4: 2040 + 680 = 2720
Step 5: 2720 + 680 = 3400
Step 6: 3400 + 680 = 4080
Step 7: 4080 + 680 = 4760
Step 8: 4760 + 680 = 5440
Step 9: 5440 + 680 = 6120
Step 10: 6120 + 680 = 6800
Step 11: 6800 + 680 = 7480
Step 12: 7480 + 680 = 8160
Step 13: 8160 + 680 = 8840
Step 14: 8840 + 680 = 9520
Step 15: 9520 + 680 = 10200
Step 16: 10200 + 680 = 10880

So, 680*16 = 10880