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goldfiish [28.3K]

4 years ago

12

A car traveling 70 miles per hour travelled one hour longer than a truck traveling 60 miles per hour. If the car and truck trave

lled a total of 330 miles, for how many hours did the car and truck travel all together?

1 answer:

Mumz [18]4 years ago

4 0

Answer:

5

Step-by-step explanation:

60 x + 70(x+1)=330

60x+70x+70=330

130x=260

x=2

x+1=3

so the answer is 5 hope i helped <33

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PLEASE HELP ME WITH THESE 2 QUESTIONS YOU GUYS, I AM TRYING TO PASS MATH CLASS. PLEASE. please. I AM GIVING 30 PTS FOR THIS. PLE

Bad White [126]

Explicit Formula

Just in case you don't know what this is, the explicit formula is the formula that solves for any term in the series without necessarily knowing what came before the term you are solving.

<em><u>Givens</u></em>

d = t_(n + 1) - t_n You can take any term and the next term for this part of the formula

d = t_3 - t_2

t_3 = 1

t_2 = -7

d = 1 - - 7 = 8

a = -15

<em><u>Formula</u></em>

t_n = a + (n - 1)*d

t_n = -15 + (n - 1)*8

For example find the 5th term.

t_5 = - 15 + (5 - 1)*8

t_5 = - 15 + 4 *8

t_5 = -15 + 32

t_5 = 17 Which is what you have.

Recursive Formula

Computers really like this formula. They use it in what is called a subroutine and they pass values from one part of the program to a subroutine which evaluates the given and sends the result back. I'm telling you all this so you see why you are doing it. The disadvantage of it for humans is that you must know the preceding term to use the recursive formula.

<em><u>Formula</u></em>

t_n = t_(n - 1) + d

<em><u>Example</u></em>

t_6 = t_(6 - 1) + d

t_6 = t_5 + 8

t_6 = 17 + 8

t_6 = 25

You can check this by using the explicit formula.

4 0

3 years ago

Read 2 more answers

Need this picture solved I don't know

Alika [10]

What item do you want the most? Once you tell me this I can write your whole essay.

8 0

3 years ago

Jack and Jill fetched 24 pints of water in their bucket. Jill drank a tenth of this, jack a quarter. They gave three eighths to

Minchanka [31]

Answer: See explanation

Step-by-step explanation:

Total water fetched = 24 pints.

Jill drank a tenth of this. This will be:

= 1/10 × 24

= 2.4 pints

Jack drank a quarter. This will be:

= 1/4 × 24 = 6.

They gave three eighths to dame Dob . Thus will be:

= 3/8 × 24

= 9

They gave a fifth to jill's mother. This will be:

= 1/5 × 24.

= 4.80

Amount that'll be left over will be:

= 24 - (2.40 + 6 + 9 + 4.80)

= 24 - 22.2

= 1.8

1.8 pints of water will be left over.

4 0

3 years ago

What is the answer to 1. please explain!

ziro4ka [17]

The answer is given below:

8 0

4 years ago

Read 2 more answers

Let $$X_1, X_2, ...X_n$$ be uniformly distributed on the interval 0 to a. Recall that the maximum likelihood estimator of a is $

Solnce55 [7]

Answer:

a) $\hat a = max(X_i)$

For this case the value for $\hat a$ is always smaller than the value of a, assuming $X_i \sim Unif[0,a]$ So then for this case it cannot be unbiased because an unbiased estimator satisfy this property:

$E(a) - a= 0$ and that's not our case.

b) $E(\hat a) - a= \frac{na}{n+1} - a = \frac{na -an -a}{n+1}= \frac{-a}{n+1}$

Since is a negative value we can conclude that underestimate the real value a.

$\lim_{ n \to\infty} -\frac{1}{n+1}= 0$

c) $P(Y \leq y) = P(max(X_i) \leq y) = P(X_1 \leq y, X_2 \leq y, ..., X_n\leq y)$

And assuming independence we have this:

$P(Y \leq y) = P(X_1 \leq y) P(X_2 \leq y) .... P(X_n \leq y) = [P(X_1 \leq y)]^n = (\frac{y}{a})^n$

$f_Y (Y) = n (\frac{y}{a})^{n-1} * \frac{1}{a}= \frac{n}{a^n} y^{n-1} , y \in [0,a]$

e) On this case we see that the estimator $\hat a_1$ is better than $\hat a_2$ and the reason why is because:

$V(\hat a_1) > V(\hat a_2)$

$\frac{a^2}{3n}> \frac{a^2}{n(n+2)}$

$n(n+2) = n^2 + 2n > n +2n = 3n$ and that's satisfied for n>1.

Step-by-step explanation:

Part a

For this case we are assuming $X_1, X_2 , ..., X_n \sim U(0,a)$

And we are are ssuming the following estimator:

$\hat a = max(X_i)$

For this case the value for $\hat a$ is always smaller than the value of a, assuming $X_i \sim Unif[0,a]$ So then for this case it cannot be unbiased because an unbiased estimator satisfy this property:

$E(a) - a= 0$ and that's not our case.

Part b

For this case we assume that the estimator is given by:

$E(\hat a) = \frac{na}{n+1}$

And using the definition of bias we have this:

$E(\hat a) - a= \frac{na}{n+1} - a = \frac{na -an -a}{n+1}= \frac{-a}{n+1}$

Since is a negative value we can conclude that underestimate the real value a.

And when we take the limit when n tend to infinity we got that the bias tend to 0.

$\lim_{ n \to\infty} -\frac{1}{n+1}= 0$

Part c

For this case we the followng random variable $Y = max (X_i)$ and we can find the cumulative distribution function like this:

$P(Y \leq y) = P(max(X_i) \leq y) = P(X_1 \leq y, X_2 \leq y, ..., X_n\leq y)$

And assuming independence we have this:

$P(Y \leq y) = P(X_1 \leq y) P(X_2 \leq y) .... P(X_n \leq y) = [P(X_1 \leq y)]^n = (\frac{y}{a})^n$

Since all the random variables have the same distribution.

Now we can find the density function derivating the distribution function like this:

$f_Y (Y) = n (\frac{y}{a})^{n-1} * \frac{1}{a}= \frac{n}{a^n} y^{n-1} , y \in [0,a]$

Now we can find the expected value for the random variable Y and we got this:

$E(Y) = \int_{0}^a \frac{n}{a^n} y^n dy = \frac{n}{a^n} \frac{a^{n+1}}{n+1}= \frac{an}{n+1}$

And the bias is given by:

$E(Y)-a=\frac{an}{n+1} -a=\frac{an-an-a}{n+1}= -\frac{a}{n+1}$

And again since the bias is not 0 we have a biased estimator.

Part e

For this case we have two estimators with the following variances:

$V(\hat a_1) = \frac{a^2}{3n}$

$V(\hat a_2) = \frac{a^2}{n(n+2)}$

On this case we see that the estimator $\hat a_1$ is better than $\hat a_2$ and the reason why is because:

$V(\hat a_1) > V(\hat a_2)$

$\frac{a^2}{3n}> \frac{a^2}{n(n+2)}$

$n(n+2) = n^2 + 2n > n +2n = 3n$ and that's satisfied for n>1.

8 0

4 years ago