Um I think your teacher might be high
-6,-7, and -8, this is more of a guess and check question
Answer:
a) the probability of A students study for more than 10 hours per week
P(X>10) = 0.117
b) The probability that an student spends between 7 and 9 hour
P(7<x< 9) = 0.9522
Step-by-step explanation:
Step(I):-
Let 'X' be random variable of the normal distributed with a mean of 7.5 hours and standard deviation of 2.1 hours
mean of the Population is = 7.5 hours
standard deviation of the Population = 2.1 hours
Z = 1.1904
The probability of A students study for more than 10 hours per week
P(X>10) = 0.5-A(Z₁) = 0.5 -A(1.1904) = 0.5 - 0.3830 = 0.117
Step(ii):-
Put x=7
put x=9
The probability that an A student spends between 7 and 9 hour
P(7 < x< 9) = A(9) - A(7)
= 0.7142 +0.238
= 0.9522
Answer:
9,942 bacteria were there at 10 hours.
Step-by-step explanation:
Equation for population decay:
The equation for population decay, after t hours, is given by:
In which P(0) is the initial population and r is the decay rate, as a decimal.
Researchers recorded that a certain bacteria population declined from 200,000 to 900 in 18 hours.
This means that and that when . So we use this to find r.
So
At this rate of decay, how many bacteria was there at 10 hours?
This is P(10). So
Rounding to the nearest whole number:
9,942 bacteria were there at 10 hours.
I think that the answer is B,