All you ever have to do is multiply the base and the length and divide by 2, so it would look like this... 8x3÷2 which would be 12
Answer:
We should expect 25 generated digits in order to get a fifth "4"
Step-by-step explanation:
For each generated digit, there are only two possible outcomes. Either it is a four, or it is not. The probability of a digit being a 4 is independent of other digits. So we use the binomial probability distribution 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.
The expetcted number of trials to get r sucesses, with p probability, is given by:

Assume that the calculator will generate a "4" on any given attempt with probability 0.20.
This means that 
How many total generated digits should we expect in order to get a fifth "4"
This is E when r = 5. So

We should expect 25 generated digits in order to get a fifth "4"
Hey!
So we are given that the two lines (the one you are trying to find and the other one whose equation you have been given) are perpendicular. This means that their slopes are the negative reciprocal of each other. Since the slope of the line you have been given is -3 the slope of the line that you need to find is 1/3. Using this and the point we have been given we can find the y-intercept.
-4 = (1/3)(7) + b
-4 = 7/3 + b
-19/3 = b
Since we know both the slope and the y-intercept we can write out equation:
y = (1/3)x - 19/3