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3 years ago

In a hotel a servant needs to clean 30 rooms in 3 hours. How many rooms a servant needs to clean in 6 hours

Mathematics

1 answer:

timurjin [86]3 years ago

7 0

Answer: 60 rooms

Step-by-step explanation:

because in 30 rooms is 3 hour + other 3 hour are 60 rooms. =60 rooms

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If X is a r.v. such that E(X^n)=n! Find the m.g.f. of X,Mx(t). Also find the ch.f. of X,and from this deduce the distribution of

astraxan [27]

$M_X(t)=\mathbb E(e^{Xt})$
$M_X(t)=\mathbb E\left(1+Xt+\dfrac{t^2}{2!}X^2+\dfrac{t^3}{3!}X^3+\cdots\right)$
$M_X(t)=\mathbb E(1)+t\mathbb E(X)+\dfrac{t^2}{2!}\mathbb E(X^2)+\dfrac{t^3}{3!}\mathbb E(X^3)+\cdots$
$M_X(t)=1+t+t^2+t^3+\cdots$
$M_X(t)=\displaystyle\sum_{k\ge0}t^k=\frac1{1-t}$

provided that $|t|$ .

Similarly,

$\varphi_X(t)=\mathbb E(e^{iXt})$
$\varphi_X(t)=1+it+(it)^2+(it)^3+\cdots$
$\varphi_X(t)=(1-t^2+t^4-t^6+\cdots)+it(1-t^2+t^4-t^6+\cdots)$
$\varphi_X(t)=(1+it)(1-t^2+t^4-t^6+\cdots)$
$\varphi_X(t)=\dfrac{1+it}{1+t^2}=\dfrac1{1-it}$

You can find the CDF/PDF using any of the various inversion formulas. One way would be to compute

$F_X(x)=\displaystyle\frac12+\frac1{2\pi}\int_0^\infty\frac{e^{itx}\varphi_X(-t)-e^{-itx}\varphi_X(t)}{it}\,\mathrm dt$

The integral can be rewritten as

$\displaystyle\int_0^\infty\frac{2i\sin(tx)-2it\cos(tx)}{it(1+t^2)}\,\mathrm dt$

so that

$F_X(x)=\displaystyle\frac12+\frac1{2\pi}\int_0^\infty\frac{\sin(tx)-t\cos(tx)}{t(1+t^2)}\,\mathrm dt$

There are lots of ways to compute this integral. For instance, you can take the Laplace transform with respect to $x$ , which gives

$\displaystyle\mathcal L_s\left\{\int_0^\infty\frac{\sin(tx)-t\cos(tx)}{t(1+t^2)}\,\mathrm dt\right\}=\int_0^\infty\frac{1-s}{(1+t^2)(s^2+t^2)}\,\mathrm dt$
$=\displaystyle\frac{\pi(1-s)}{2s(1+s)}$

and taking the inverse transform returns

$F_X(x)=\dfrac12+\dfrac1\pi\left(\dfrac\pi2-\pi e^{-x}\right)=1-e^{-x}$

which describes an exponential distribution with parameter $\lambda=1$ .

6 0

3 years ago

5(4+3√24-5(8+9÷3)³<br>ayuds

vichka [17]

Answer: -33255 + 30 $\sqrt{6}$

Step-by-step explanation:

6 0

3 years ago

Pls pls pls pls answer RIGHT

Korolek [52]

Answer:

2nd one i think

Step-by-step explanation:

7 0

3 years ago

Read 2 more answers

Can you prove this congruent? Using what theorem/postulate?

slavikrds [6]

I'd say that, if the angles S and U are equal, as the SV and UV segments move towards each other, they meet at vertex V, the angles they make, angle SVT and UVT, have to be equal, because the side TV is shared by both, and has the same direction.

now, side TV is on both triangles, and is shared by both, so is the same length, so TV on one triangle is equal to TV on the other

check the picture below

so, you have one Angle, another Angle, and then a Side
A A S

3 0

3 years ago

A company has 875 employees. "Half - Price Wednesday," 64% of the employees eat lunch at the company cafeteria. How many employe

Vika [28.1K]

875 × .64= 560

answer: 560 employees eat lunch at the cafeteria on Wednesday.

4 0

4 years ago

Read 2 more answers