OK, let's crack this. We're given 16 and our task is to multiply it by 20. Essentially, we'll be adding 16 to itself 20 times.
Step 1: 0 + 16 = 16
Step 2: 16 + 16 = 32
Step 3: 32 + 16 = 48
Step 4: 48 + 16 = 64
Step 5: 64 + 16 = 80
Step 6: 80 + 16 = 96
Step 7: 96 + 16 = 112
Step 8: 112 + 16 = 128
Step 9: 128 + 16 = 144
Step 10: 144 + 16 = 160
Step 11: 160 + 16 = 176
Step 12: 176 + 16 = 192
Step 13: 192 + 16 = 208
Step 14: 208 + 16 = 224
Step 15: 224 + 16 = 240
Step 16: 240 + 16 = 256
Step 17: 256 + 16 = 272
Step 18: 272 + 16 = 288
Step 19: 288 + 16 = 304
Step 20: 304 + 16 = 320

So, 16*20 = 320