Answer:
30
Step-by-step explanation:
12 is 40% of the total number of cards.
12 = 0.4x, where x is total number of cards
/0.4 /0.4
30 = x
30 cards
Answer:
0.7061 = 70.61% probability she will have her first crash within the first 30 races she runs this season
Step-by-step explanation:
For each race, there are only two possible outcomes. Either the person has a crash, or the person does not. The probability of having a crash during a race is independent of whether there was a crash in any other race. This means that the binomial probability distribution is used to solve this question.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.

In which
is the number of different combinations of x objects from a set of n elements, given by the following formula.

And p is the probability of X happening.
A certain performer has an independent .04 probability of a crash in each race.
This means that 
a) What is the probability she will have her first crash within the first 30 races she runs this season
This is:

When 
We have that:



0.7061 = 70.61% probability she will have her first crash within the first 30 races she runs this season
Answer:
multiply by feet per mile and divide by seconds per hour
Step-by-step explanation:
To get the desired units, multiply by a factor that is equal to 1, but has the desired units in the numerator and the units you're converting from in the denominator.
For units in the denominator that you want to change, use the inverse of the above multiplier.
We have miles/hour, which has miles in the numerator. We want feet/second, which has feet in the numerator, so we need to multiply by the ratio of feet per mile: 5280 ft/mi.
We also have hours in the denominator, where we want seconds. So, we divide by the factor 3600 s/h.

I believe the answer is 1/2 because 5 out of 10 of the trials have 0 occurring more than once so the fraction is 5/10= 1/2 so I think you answer should be 1/2