Joe is 5 years older than Sydney. The sum of their ages is 45. What is Sydney’s age?

Mathematics

1 answer:

sweet-ann [11.9K]3 years ago

8 0

Answer:

20 years old

Step-by-step explanation:

Joe = J

Sydney = S

J = 5 + S

J + S = 45

Substitute

5 + S + S = 45

Add

5 + 2S = 45

Subtract 5 from both sides of the equation

2S = 40

Divide both sides of the equation by 2

S = 20

Sydney is 20 years old

Hope this helps :)

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4-It has been a bad day for the market, with 70% of securities losing value. You are evaluating a portfolio of 20 securities and

riadik2000 [5.3K]

Answer:

b) 0.0007

c) 0.4163

d) 0.2375

Step-by-step explanation:

We are given the following:

We treat securities lose value as a success.

P(Security lose value) = 70% = 0.7

Then the securities lose value follows a binomial distribution, where

$P(X=x) = \binom{n}{x}.p^x.(1-p)^{n-x}$

where n is the total number of observations, x is the number of success, p is the probability of success.

Now, we are given n = 20.

a) Assumptions

There are 20 independent trials.
Each trial have two possible outcome: security loose value or security does not lose value.
The probability for success of each trial is same, p = 0.7

b) P(all 20 securities lose value)

We have to evaluate:

$P(x = 20)\\= \binom{20}{0}(0.7)^0(1-0.7)^{20}\\= 0.0007$

0.0007 is the probability that all 20 securities lose value.

c) P(at least 15 of them lose value.)

$P(x \geq 15)\\= P(x=15) + P(x = 16) + P(x=17) + P(x=18) +P(x = 19) +P(x = 20)\\ \binom{20}{15}(0.7)^{15}(1-0.7)^{5} +...+ \binom{20}{20}(0.7)^{20}(1-0.7)^{0} \\=0.4163$