You need to read the explanation for the German Tank method (http://www.guardian.co.uk/g2/story/0,,1824525,00.html http://www.guardian.co.uk/g2/story/0,,1824525

You need to read the explanation for the German Tank method (http://www.guardian.co.uk/g2/story/0,,1824525,00.html http://www.guardian.co.uk/g2/story/0,,1824525,00.html) to see the formula used to get 104.