Let Hannah = X and Heather = Y.
The sum of their ages is 30, so you would have x + y = 30
Then Hannah's age is 4 less than 2 times Heather's age so X = 2y-4
The equations are :
X + Y = 30 and X = 2y - 4
The answer is C.
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.
See the venn-diagram in the picture.
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Answer:
CED = 117
Step-by-step explanation:
21x +21 = 7x +49
21x - 7x = 49 - 21
14x = 28
x = 28/14
x = 2
7x + 49
=7(2) + 49
=14 + 49
=63
180 -63 = 117
CED= 117
Answer:
9x + 5y
Step-by-step explanation:
Here, in 2x + 5y+ 7x, the 'like terms' are 2x and 7x, and the sum of these terms is 9x. Thus, 2x + 5y+ 7x becomes 9x + 5y.
