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3 years ago

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Mathematics

1 answer:

kvv77 [185]3 years ago

3 0

Answer:

Step-by-step explanation:

yellow was picked more times then green so the percent would be more then 50.

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Ishaan is 222 times as old as Christopher. 353535 years ago, Ishaan was 777 times as old as Christopher.

klemol [59]

<h3><u>Question:</u></h3>

Ishaan is 2 times as old as Christopher. 35 years ago, Ishaan was 7 times as old as Christopher. How old is Christoper now?

<h3><u>Answer:</u></h3>

The present age of Christoper is 42 years old

<h3><u>Solution:</u></h3>

Given that Ishaan is 2 times as old as Christoper

Let the present age of Christoper be "x"

Then, Present age of Ishaan = 2 times as old as Christoper

present age of Ishaan = 2x

<em><u>35 years ago, Ishaan was 7 times as old as Christopher</u></em>

Age of Ishaan 35 years ago = Present age of Ishaan - 35

Age of Ishaan 35 years ago = 2x - 35

Similarly,

Age of christoper 35 years ago = Present age of christoper - 35

Age of christoper 35 years ago = x - 35

From given statement, 35 years ago, Ishaan was 7 times as old as Christopher

Age of Ishaan 35 years ago = 7 times the age of Christoper 35 years ago

(2x - 35) = 7(x - 35)

<em><u>Solve the above equation for "x"</u></em>

2x - 35 = 7x - 245

2x - 7x = -245 + 35

-5x = -210

Thus present age of Christoper is 42 years old

5 0

3 years ago

At 82°F, a certain insect chirps at a rate of 61 times per minute, and at 91°F, they chirp 124 times per minute. Write an equati

Ganezh [65]

Answer:

$y=7x-513$

Step-by-step explanation:

Let

x----> the temperature in degrees Fahrenheit

y ---->insect chirping rate in times per minute

we have the ordered pairs

(82,61) and (91,124)

step 1

Find the slope

The formula to calculate the slope between two points is equal to

$m=\frac{y2-y1}{x2-x1}$

substitute the values

$m=\frac{124-61}{91-82}$

$m=\frac{63}{9}=7$

step 2

Find the equation of the line

we know that

The equation in slope intercept form is equal to

$y=mx+b$

where

m is the slope

b is the y-intercept

we have

$m=7$ ---> the units are chirps per minute/degree F

take the point (82,61)

substitute and solve for b

$61=7(82)+b$

$61=574+b$

$b=-513$

substitute

$y=7x-513$

4 0

3 years ago

Let X and Y be discrete random variables. Let E[X] and var[X] be the expected value and variance, respectively, of a random vari

Ulleksa [173]

Answer:

(a) $E[X+Y]=E[X]+E[Y]$

(b) $Var(X+Y)=Var(X)+Var(Y)$

Step-by-step explanation:

Let X and Y be discrete random variables and E(X) and Var(X) are the Expected Values and Variance of X respectively.

(a)We want to show that E[X + Y ] = E[X] + E[Y ].

When we have two random variables instead of one, we consider their joint distribution function.

For a function f(X,Y) of discrete variables X and Y, we can define

$E[f(X,Y)]=\sum_{x,y}f(x,y)\cdot P(X=x, Y=y).$

Since f(X,Y)=X+Y

$E[X+Y]=\sum_{x,y}(x+y)P(X=x,Y=y)\\=\sum_{x,y}xP(X=x,Y=y)+\sum_{x,y}yP(X=x,Y=y).$

Let us look at the first of these sums.

$\sum_{x,y}xP(X=x,Y=y)\\=\sum_{x}x\sum_{y}P(X=x,Y=y)\\\text{Taking Marginal distribution of x}\\=\sum_{x}xP(X=x)=E[X].$

Similarly,

$\sum_{x,y}yP(X=x,Y=y)\\=\sum_{y}y\sum_{x}P(X=x,Y=y)\\\text{Taking Marginal distribution of y}\\=\sum_{y}yP(Y=y)=E[Y].$

Combining these two gives the formula:

$\sum_{x,y}xP(X=x,Y=y)+\sum_{x,y}yP(X=x,Y=y) =E(X)+E(Y)$

Therefore:

$E[X+Y]=E[X]+E[Y] \text{ as required.}$

(b)We want to show that if X and Y are independent random variables, then:

$Var(X+Y)=Var(X)+Var(Y)$

By definition of Variance, we have that:

$Var(X+Y)=E(X+Y-E[X+Y]^2)$

$=E[(X-\mu_X +Y- \mu_Y)^2]\\=E[(X-\mu_X)^2 +(Y- \mu_Y)^2+2(X-\mu_X)(Y- \mu_Y)]\\$Since we have shown that expectation is linear$\\=E(X-\mu_X)^2 +E(Y- \mu_Y)^2+2E(X-\mu_X)(Y- \mu_Y)]\\=E[(X-E(X)]^2 +E[Y- E(Y)]^2+2Cov (X,Y)$

Since X and Y are independent, Cov(X,Y)=0

$=Var(X)+Var(Y)$

Therefore as required:

$Var(X+Y)=Var(X)+Var(Y)$

7 0

3 years ago

The volume of a cube is 36 cubic feet. What is the volume of a pyramid that fits exactly inside the cube?

jok3333 [9.3K]

Volume of a cube = 1/3 volume of cube = 1/3 * 36 = 12 cubic feet.

6 0

3 years ago

F(x) = -6x-1<br> f(-1/2) = ?

UNO [17]

Answer:

Intersection point of this is (0,-0.5)

Step-by-step explanation:

Hope this helps :)

7 0

3 years ago