Separate post, but I wanted to look at the radiation question as a separate maths problem. Suppose that we're not talking linear multiplication of percentage chances, let's look at it as an aggregate of smaller chances. Each "unit" of radiation would have a chance of mutating you. You can't just linearly add up the chances either, since you're double-counting people who were mutated "twice" by different exposures.
So, the high-mutation family is more susceptible to the radiation, but it's not 11.6 times as likely, it's 11.6 times the exposure. The actual chance is an aggregate sum of the effects of smaller exposures. But, if we're making this assumption for the high-mutation family, we also need to make the same assumption for the low-mutations families: the chance is not a linear multiple. So first, let's work out how many multiples of the "background" radiation each person living near the radioactive waste is exposed to, just to be consistent.
The way you work this out is to work out the chance of NOT being mutated by a single exposure, and put this number to the power of the number of exposures. Then subtract the result from 1, and there's your probability (p) of being mutated at least once. This way, we can work out how many "background level" exposures you'd need to have to be mutated at least once, if you live at the waste dump:
p = 1 - (999/1000)^n
p = 0.0116 and we want to solve for 'n'
0.0116 = 1 - (999/1000)^n
(999/1000)^n = 1 - 0.0116
log((999/1000)^n) = log(1 - 0.0116)
n log(999/1000) = log(1 - 0.0116)
n = log(1 - 0.0116) / log(999/1000)
n = 11.66... units of radiation. A little bit more than 11.6 times the radiation.
But the "susceptible" family has a base rate of 0.1 mutations per unit of radiation. So, their chance of not being mutated by a single dose is 9/10. We need to work out 'p' for this family:
p = 1 - (9/10)^11.66
p = 1 - 00.29266953
p = 0.7073 or 70.73% chance of being mutated.
But of course, this is not the same thing as where we said "multiply the chance". The amount of exposure given here multiplies the chance of mutation by 7, not 11.6.