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2 years ago

How many palindromes between 1000 and 9999 inclusive are divisible by 9?

Mathematics

1 answer:

Serhud [2]2 years ago

5 0

Palindromes are numbers that remain the same, when reversed.

There are 10 palindromes divisible by 9 between 1000 and 9999

To do this, we list the numbers divisible by 9 between 10 and 99.

The numbers are:

$\mathbf{A = 09,\ 18,\ 27,\ 36,\ 45.\ 54,\ 63,\ 72,\ 81,\ 90,\ 99}$

Flip these numbers

$\mathbf{B =90,\ 81,\ 72,\ 63,\ 54.\ 45,\ 36,\ 27,\ 18,\ 09,\ 99}$

Combine corresponding numbers

$\mathbf{AB =0990,\ 1881,\ 2772,\ 3663,\ 4554,\5445,\ 6336,\ 7227,\ 8118,\ 9009,\ 9999}$

Rewrite as:

$\mathbf{AB =990,\ 1881,\ 2772,\ 3663,\ 4554,\5445,\ 6336,\ 7227,\ 8118,\ 9009,\ 9999}$

990 is less than 1000.

So, we have:

$\mathbf{AB =1881,\ 2772,\ 3663,\ 4554,\5445,\ 6336,\ 7227,\ 8118,\ 9009,\ 9999}$

Count the numbers

$\mathbf{n(AB) =10}$

Hence, there are 10 palindromes divisible by 9 between 1000 and 9999

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mr_godi [17]

To find the perimeter, the equation is (w2 + l2 = p)

Where w is width and l is length and p is perimeter.

If you have the width, then you double it for both widths.

Then subtract that number from the perimeter.

150-60 = 90

90 is the remaining number for the lengths. Since both lengths needs to be equal, you split the 90. 45.

You length equals 45.

45(2) + 30(2) = Perimeter of 150.

Your answer is 45.

7 0

2 years ago

13....................

Mashcka [7]

13.

(a)

$y=-5x^2+21x-3$

for x = 2:

$y=-5(2)^2+21(2)-3=-20+42-3=19$

for x = 5

$y=-5(5)^2+21(5)-3=-125+105-3=-23$

(b)

The graph is:

(c)

Using the graph:

$\begin{gathered} x=1.8,y=18.6 \\ x=0.548,y=7 \\ x=3.65,y=7 \end{gathered}$ $\begin{gathered} x=1.8 \\ y=-5(1.8)^2+21(1.8)-3=-16.2+37.8-3=18.6 \end{gathered}$ $\begin{gathered} y=7 \\ -5x^2+21x-3=7 \\ -5x^2+21x-10=0 \end{gathered}$

Using the quadratic formula:

$\begin{gathered} x=\frac{-b\pm\sqrt[]{b^2-4ac}}{2a} \\ x=\frac{-21\pm\sqrt[]{21^2-4(-5)(-10)}}{2(-5)} \\ x=\frac{-21\pm\sqrt[]{241}}{-10} \\ x=0.54758 \\ or \\ x=3.6524 \end{gathered}$

6 0

9 months ago

In a triangle, the measure of the first angle is twice the measure of the second angle. The measure of third angle os 88 degrees

Volgvan

Answer:

Answers: 46, 23, and 111

Step-by-step explanation:

To answer, we need to know the angles. Therefore, give each angle a name. Angle 1 will be x, 2 will be y, 3 will be z. So, using this system of equations:

x=2y

z=y+88

x+y+z=180

Substituting, z = 1/2(x)+88, now plug z into the third equation:

x+1/2(x)+1/2(x)+88=180

this simplifies to 2x+88=180

subtracting 88 from both sides leaves 2x=92

x=46

plug this in to the first equation: 46 = 2y, so y = 23

plug this into the third one leaves z = 111

Hope this helps!

3 0

2 years ago

Let f be defined by the function f(x) = 1/(x^2+9)

riadik2000 [5.3K]

(a)

$\displaystyle\int_3^\infty \frac{\mathrm dx}{x^2+9}=\lim_{b\to\infty}\int_{x=3}^{x=b}\frac{\mathrm dx}{x^2+9}$

Substitute x = 3 tan(t ) and dx = 3 sec²(t ) dt :

$\displaystyle\lim_{b\to\infty}\int_{t=\arctan(1)}^{t=\arctan\left(\frac b3\right)}\frac{3\sec^2(t)}{(3\tan(t))^2+9}\,\mathrm dt=\frac13\lim_{b\to\infty}\int_{t=\arctan(1)}^{t=\arctan\left(\frac b3\right)}\mathrm dt$

$=\displaystyle \frac13 \lim_{b\to\infty}\left(\arctan\left(\frac b3\right)-\arctan(1)\right)=\boxed{\dfrac\pi{12}}$

(b) The series

$\displaystyle \sum_{n=3}^\infty \frac1{n^2+9}$

converges by comparison to the convergent p-series,

$\displaystyle\sum_{n=3}^\infty\frac1{n^2}$

$\displaystyle \sum_{n=1}^\infty \frac{(-1)^n (n^2+9)}{e^n}$

converges absolutely, since

$\displaystyle \sum_{n=1}^\infty \left|\frac{(-1)^n (n^2+9)}{e^n}\right|=\sum_{n=1}^\infty \frac{n^2+9}{e^n} < \sum_{n=1}^\infty \frac{n^2}{e^n} < \sum_{n=1}^\infty \frac1{e^n}=\frac1{e-1}$

That is, ∑ (-1)ⁿ (n ² + 9)/eⁿ converges absolutely because ∑ |(-1)ⁿ (n ² + 9)/eⁿ| = ∑ (n ² + 9)/eⁿ in turn converges by comparison to a geometric series.

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2 years ago

It is proposed to build a raft of pine logs for carrying a cargo on a river. The cargo will weigh 500 kg, and it must be kept en

siniylev [52]

Answer:

They will need 200kg of pine logs.

Gauge pressure in the tank = 24045.29 Pa

Absolute pressure= 125370.29Pa

Step-by-step explanation:

Full question:sp.gr=0.8.The fluid in the nanometer is ethyl iodide with sp.gr =1.93. The manometric fluid height is 50 inches. What is the gauge pressure and absolute pressure in the tank?

Converting 50inches to metres. Multiply by 0.0254

50×0.0254=1.27m

Gauge pressure in tank is given by:

P = pgh

Where p= density,g= acceleration due to gravity, h= height

P= 1.93× 1000× 9.81× 1.27= 24045.29Pa

Absolute pressure=Ptotal= Pliquid + Patm

Absolute pressure =24045.29 + 101325=125370.29pa

6 0

3 years ago