It is not necessary: some people find it easier to do so, others do not.
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take out zeros
You annex zeros to get the answer. Such as 0.03 equals 0.030, and you keep annexing zeros to the end to get your answer. Until you get to the hundred thousandths place.
The product may not have any zeros if there are "carries" from a product at a lower level.
3500-- so 2 zeros
Why will there 2 zeroes in the the product of 60X90