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3 years ago

14

On Tuesday,620 students attended a middle school.A survey showed that 341 students brought lunch to school the day . What percen

t of the students brought their lunches.

1 answer:

irina1246 [14]3 years ago

3 0

55%

Mark brainliest please

Hope this helps you

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Who was the first person to invent the Commutative Property?

dimulka [17.4K]

Francois Servois in 1814

5 0

3 years ago

Write -4i+(1/4-5i)-(-3/4+8i)+17i as a complex number in the standard for

KatRina [158]

Answer:

$1+ 0i$

Step-by-step explanation:

A complex number is a number which has some real part and some imaginary part.

Standard form of a complex number is represented as

$a +bi$

Where $a$ is the real part,

and $bi$ is the imaginary part.

And $i = \sqrt{-1}$

Given complex number:

$-4i+\dfrac{1}{4}-5i)-(-\dfrac{3}{4}+8i)+17i\\\Rightarrow -4i+\dfrac{1}{4}-5i + \dfrac{3}{4}-8i+17i\\\Rightarrow \dfrac{3}{4}+\dfrac{1}{4}-4i -5i-8i+17i\\\Rightarrow \dfrac{3+1}{4}-17i+17i\\\Rightarrow \dfrac{4}{4}+0i\\\Rightarrow 1 + 0i$

Hence, the standard form is $1+ 0i$ .

8 0

3 years ago

Y''+y'+y=0, y(0)=1, y'(0)=0

mars1129 [50]

Answer:

$y=e^{\frac{-t}{2}}\left ( \cos\left ( \frac{\sqrt{3}t}{2} \right )+\frac{1}{\sqrt{3}}\sin \left ( \frac{\sqrt{3}t}{2} \right ) \right )$

Step-by-step explanation:

A second order linear , homogeneous ordinary differential equation has form $ay''+by'+cy=0$ .

Given: $y''+y'+y=0$

Let $y=e^{rt}$ be it's solution.

We get,

$\left ( r^2+r+1 \right )e^{rt}=0$

Since $e^{rt}\neq 0$ , $r^2+r+1=0$

{ we know that for equation $ax^2+bx+c=0$ , roots are of form $x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}$ }

We get,

$y=\frac{-1\pm \sqrt{1^2-4}}{2}=\frac{-1\pm \sqrt{3}i}{2}$

For two complex roots $r_1=\alpha +i\beta \,,\,r_2=\alpha -i\beta$ , the general solution is of form $y=e^{\alpha t}\left ( c_1\cos \beta t+c_2\sin \beta t \right )$

i.e $y=e^{\frac{-t}{2}}\left ( c_1\cos\left ( \frac{\sqrt{3}t}{2} \right )+c_2\sin \left ( \frac{\sqrt{3}t}{2} \right ) \right )$

Applying conditions y(0)=1 on $e^{\frac{-t}{2}}\left ( c_1\cos\left ( \frac{\sqrt{3}t}{2} \right )+c_2\sin \left ( \frac{\sqrt{3}t}{2} \right ) \right )$ , $c_1=1$

So, equation becomes $y=e^{\frac{-t}{2}}\left ( \cos\left ( \frac{\sqrt{3}t}{2} \right )+c_2\sin \left ( \frac{\sqrt{3}t}{2} \right ) \right )$

On differentiating with respect to t, we get

$y'=\frac{-1}{2}e^{\frac{-t}{2}}\left ( \cos\left ( \frac{\sqrt{3}t}{2} \right )+c_2\sin \left ( \frac{\sqrt{3}t}{2} \right ) \right )+e^{\frac{-t}{2}}\left ( \frac{-\sqrt{3}}{2} \sin \left ( \frac{\sqrt{3}t}{2} \right )+c_2\frac{\sqrt{3}}{2}\cos\left ( \frac{\sqrt{3}t}{2} \right )\right )$

Applying condition: y'(0)=0, we get $0=\frac{-1}{2}+\frac{\sqrt{3}}{2}c_2\Rightarrow c_2=\frac{1}{\sqrt{3}}$

Therefore,

$y=e^{\frac{-t}{2}}\left ( \cos\left ( \frac{\sqrt{3}t}{2} \right )+\frac{1}{\sqrt{3}}\sin \left ( \frac{\sqrt{3}t}{2} \right ) \right )$

3 0

3 years ago

If the Revenue for the week is $2000, and labor cost consists of two workers earning $8 per hour who work 40 hours each, what is

Hatshy [7]

2 workers, each 8 per hour, for 40hrs a week, so one earns 8 * 40, or 320 bucks, is two workers, so 320 + 320 or 640 bucks

if 2000 is the 100%, how much is 640 in percentage off of it?

well $\bf \begin{array}{ccllll}
amount&\%\\
\textendash\textendash\textendash\textendash\textendash\textendash&\textendash\textendash\textendash\textendash\textendash\textendash\\
2000&100\\ 640&x
\end{array}\implies \cfrac{2000}{640}=\cfrac{100}{x}$

solve for "x"

7 0

3 years ago

Read 2 more answers

How do you explain a ratio in words?<br><br> For example, 6:13

Pavel [41]

It’s like a fraction in simplest form, but the fraction bar is replaced horizontally with a “to”, or a colon.
Hope this helps!

4 0

3 years ago