Let be the 20 marks of the boys, and
be the 10 marks of the girls.
We know that the global mean was 70, meaning that
Multiplying both sides by 30 we deduce that the sum of the scores of the whole classroom is
By the same logic, we work with the marks of the boys alone: we know the average:
And we deduce the sum of the marks for the boys:
Which implies that the sum of the marks of the girls is
And finally, the mean for the girls alone is
The -3 is not in the exponent
Explanation:
The parent function is . Plugging in x = 0 leads to y = 1. So the point (0,1) is on the f(x) curve. Going from (0,1) to (0,-2) is a vertical shift of 3 units downward. To represent this shift, we tack on a "-3" at the end of the f(x) function.
You could look at other points as well, but I find working with x = 0 is easiest.
As a check, plugging x = 0 into g(x) leads to...
This confirms our answer.
Answer:
0.0656
Step-by-step explanation:
For each message, we have these following probabilities:
90% probability it is spam.
10% probability it is legitimate.
Compute the probability that the first legitimate e-mail she finds is the fifth message she checks:
The first four all spam, each with a 90% probability.
The fifth legitimate, with a 10% probability.