If you take out the last two zeroes of the numbers you are multiplying, you get 5*8 and 3*4. The first product is 40, the second is 12. So the extra zero is from 40. 5 times an even number always has a zero on the end, because an even number is a number divisible by 2 and 5 times 2 is 10; so that's where the extra zero comes from. Put the two zeroes back on the products and we have 4000 and 1200.