Teacher Discussion Forums

Hello, I'd like you to help me to get to explain my students how to write that figure.
Some of them say that 3 x 1.5mis equal to 1.5000000
And some say 3 x 1.500000
For me the result is the second choice, but I can't find good reason for that, because those who are for the first one are people who studied economics and maths, and they have clear in mind their opinion.
Could you help me to find a good reason to convince them, please?
Thank you in advance

are they not recognising the .5 as half a million? When I taught basic math I asked them how much they thought .5 million was. If .5 million is 500 thousand or 500000, then it follows that 1.5 million is 1500000