a) The only factor with zeros is 400, which has 2 of them. Since the least-significant non-zero digits are not 2 or 5, the product 193×4 will not have any trailing zeros. Consequently, the product 193×400 = 77,200 will have 2 zeros.
b) Same reasoning, except with 3 zeros. 193×4000 = 772,000
c) The product of anything and zero is zero. There will be 1 zero in the product 193×400×0 = 0.
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If you like, you can factor out the trailing zeros:
... 193×400 = 193×4×100 = (193×4)×100 = 772×100
You can also use scientific notation to keep track of the trailing zeros. Here, the numbers end in 5 and an even number, so result in additional trailing zeros when multiplied.
... 192×500 = 192×5×10² = 960×10² = 96×10¹×10² = 96×10³ = 96000
