Hey!
Hope this helps...
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To solve this, we will be doing a semi-alternate route, but it will get us to our answer...
400 / 100 = 4
30 / 4 = 7.5 seconds
60 * 60 * 7.5 = 27,000 meters per hour
<em></em><em>Lets plug it into our meters to miles formula...</em>
27,000 / 1,609.344 ~ 16.777 miles per hour
So...
The answer is: The Polar Express was going 27,000 meters per hour (or roughly close to 16.777 miles per hour)...