A basic fact is 6x1, which everyone knows is 6. Because 6x1=6, we can use a pattern of either counting by six 100 times, or adding two zeroes at the end, which is the "zero trick".
Another example of the zero trick is 70x100, because all you have to do is 7x1=7 and then add the three zeroes at the end, which gets you 7,000.