Forum adverts like this one are shown to any user who is not logged in. Join us by filling out a tiny 3 field form and you will get your own, free, dakka user account which gives a good range of benefits to you: No adverts like this in the forums anymore. Times and dates in your local timezone. Full tracking of what you have read so you can skip to your first unread post, easily see what has changed since you last logged in, and easily see what is new at a glance. Email notifications for threads you want to watch closely. Being a part of the oldest wargaming community on the net. If you are already a member then feel free to login now.

I need some mathhammer help here.

Vendetta with 3 TL Lascannons fires on a Land Raider with the intent to either Immobilize, Wreck or Explode. What are the odds?

I can't seem to wrap my head around the fractions when including twinlinking. Help please.

What you do is you work out the odds for a single shot hitting at BS3, then deduct that from one, work out the chance of that hitting at BS3 and add the results together.

Its easier if you use a spreadsheet like excel and work in numbers rather than fractions because they can give you a percentage and are easier to figure out by looking at than fractions, and a spreadsheet does all the calculations for you, which makes things so much easier

So for a TL-Lascannon at BS3:

You have a 50% chance to hit at BS3 so,

1*0.5=0.5

Then you need to work out the chance of the missed roll hitting:

0.5*0.5=0.25

So overall,

0.5+0.25=0.75 or a 75% chance to hit with a single shot.

This is simplified of course but to work out true probabilities requires looking into distributions and actually dont tell us much more than this simple maths.

After that you can work out the chance to glance and penetrate a LR (each 1/6 cahnce, so multiply the chance to hit by 1/6) and there work out each result on the VD table (which are each again 1/6 chance)

OK.

So now we have three shots with a 75% chance to hit. How do I figure that.

And more to the point; how do I figure the armourpenetration part?

Here's an easy way to do it. First, figure out the odds of one shot.

3/4 to hit, 4/36 to at least immobilize (think of the d6 roll for pen followed by the d6 roll on the damage table as generating 36 possible outcomes. You are happy with a 5 followed by a 6, or a 6 followed by a 4, 5, or 6, for 4 total happy outcomes.)

so, we've got 3/4 to hit * 1/9 to make us happy, or 3/36 to be satisfactory, for a 1/12 chance that any given twin linked bs 3 lascannon shot on a landraider satisfies you.

We can't just mulitply this by 3, as math doesn't work that way, but we can still figure out the vendetta's total odds of getting a satisfactory result by inverting.

The odds that it won't get a satisfactory result are the odds that all 3 lascannons don't satisfy. Thus, 11/12 * 11/12 * 11/12.

1331/1728 = .770, odds of failed vendetta shot.

The odds of a good vendetta shot are 1 - the odds of a failed vendetta shot, or 1-.77, or .23. So, to sum up, you have a little less than a 1/4 chance of wrecking, exploding or immobilizing a land raider by firing a full volley from one vendetta's 3 twin linked bs 3 lascannons.

So get four similiar equivelents of long-range firing death akin to the venetta (so, another three, or perhaps a few infantry lascannons/medusa bastion breacher shot/etc) and aim it all at the landraider. If you kane it suffuiciently before all four groups have fired, peel off the shots to other targets.

Or wait a bit and use four melta's. Go crazy, make sure thier on foot (disembarked) and get a BiD order involved. Bye bye monolith ..no wait, Land raider

I like to take my results and express them as point value spent per result.

So for example, a single Vendetta is going to net approximately .25 immobilization or worse results against AV14, non-open topped.

.25/130 = roughly 520 points spent (if buying Vendettas) to halt a Land Raider.

It's the same math, but busting it out in different formats can help you make decisions about striking a suitable internal balance within your army.

Wow. Thanks guys! I have messed around with mathhammer a little bit, but I did not know about the last part about finding the inverse. This has been very informative.