Halen wrote the product 0.4 for the problem shown don says that is not correct since when you multiply by tenths the product will be in the hundredths. Is don right explain

Yes, if you multiply tenth by tenth you get hundredth. However, Don is wrong for saying Halen is wrong. This is because 0.8 x 0.5 = 8/10 x 5/10 = 40/100 = 0.40

But because the zero after 4 is insignificant, the zero goes and it is now 0.4.