When you get your first yahtzee you decide what column to take it in but you do not get a bonus for your first one.

Here is how it works dependng on the column you choose initially:

Option 1:
First yahtzee in column 1 - 50 points no bonus
Second yahtzee in column 3 - 150 points + 300 bonus
Third yahtzee in column 2 - 100 points + 200 bonus

Overall total = 800 points

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Option 2:
First yahtzee in column 2 - 100 points no bonus
Second yahtzee in column 3 - 150 points + 300 bonus
Third yahtzee in column 1 - 50 points + 100 bonus

Overall total = 700 points

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Option 3:
First yahtzee in column 3 - 150 points no bonus
Second yahtzee in column 2 - 100 points + 200 bonus
Third yahtzee in column 1 - 50 points + 100 bonus

Overall total = 600 points

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Now if you knew you were always going to get 3 yahtzees, then you would always choose option 1 to get 800 points.

But let's say you only get 2 yahtzees, scoring only the first two lines giving:
Option 1 - 500 points
Option 2 - 550 points
Option 3 - 450 points

In this case option 2 is better.

It is all on the odds.

Generally I work on the rule that if I get a yahtzee in the first 10 rolls, I'll choose option 1. If my first yahtzee is between 11 and 25, then I go for option 2. After 25 I go for option 3, roughly speaking.

In all cases fourth yahtzees get a 300 bonus.

It really is just a case of what column you take for you first yahtzee, its a bit of a gamble.