Answer:
A darts player practices throwing a dart at the bull’s eye on a dart board. Her probability of hitting the bull’s eye for each throw is 0.2.
(a) Find the probability that she is successful for the first time on the third throw:
The number F of unsuccessful throws till the first bull’s eye follows a geometric
distribution with probability of success q = 0.2 and probability of failure p = 0.8.
If the first bull’s eye is on the third throw, there must be two failures:
P(F = 2) = p
2
q = (0.8)2
(0.2) = 0.128.
(b) Find the probability that she will have at least three failures before her first
success.
We want the probability of F ≥ 3. This can be found in two ways:
P(F ≥ 3) = P(F = 3) + P(F = 4) + P(F = 5) + P(F = 6) + . . .
= p
3
q + p
4
q + p
5
q + p
6
q + . . . (geometric series with ratio p)
=
p
3
q
1 − p
=
(0.8)3
(0.2)
1 − 0.8
= (0.8)3 = 0.512.
Alternatively,
P(F ≥ 3) = 1 − (P(F = 0) + P(F = 1) + P(F = 2))
= 1 − (q + pq + p
2
q)
= 1 − (0.2)(1 + 0.8 + (0.8)2
)
= 1 − 0.488 = 0.512.
(c) How many throws on average will fail before she hits bull’s eye?
Since p = 0.8 and q = 0.2, the expected number of failures before the first success
is
E[F] = p
q
=
0.8
0.2
= 4.
Answer:
d, b + b + 3c and 2b + 3c
Step-by-step explanation:
Answer:
x = -5
Step-by-step explanation:
If g(x)= 3x - 12, and g(x)= -27 then -27 = 3x -12
Solve for x
-27 = 3x -12, add 12 to both sides
-27+12 = 3x, add -27+12
-15 = 3x, divide both sides by 3
-5 = x
60 miles /2.5 gallons is 24 miles / gallon
Let x be the no. of seconds it takes for the balloons to be at the same height.
7+3x = 12+2x
Deduct both sides by 2x.
7+x = 12
Deduct both sides by 7.
x = 5
Ans: It will take 5 seconds for the balloons to be at the same height.
