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3 years ago

What is a percentage? What do we do with percentages?

Mathematics

1 answer:

Marianna [84]3 years ago

6 0

Answer:

percentages are used like fractions and decimals, as ways to describe parts of a whole. For example, discounts in shops, bank interest rates, rates of inflation and many statistics in the media are expressed as percentages. Percentages are important for understanding the financial aspects of everyday life. When you are using percentages, the whole is considered to be made up of a hundred equal parts. The symbol % is used to show that a number is a percentage, and less commonly the abbreviation 'pct' may be used.

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Find the surface area of the solid generated by revolving the region bounded by the graphs of y = x2, y = 0, x = 0, and x = 2 ab

Nikitich [7]

Answer:

See explanation

Step-by-step explanation:

The surface area of the solid generated by revolving the region bounded by the graphs can be calculated using formula

$SA=2\pi \int\limits^a_b f(x)\sqrt{1+f'^2(x)} \, dx$

If $f(x)=x^2,$ then

$f'(x)=2x$

and

$b=0\\ \\a=2$

Therefore,

$SA=2\pi \int\limits^2_0 x^2\sqrt{1+(2x)^2} \, dx=2\pi \int\limits^2_0 x^2\sqrt{1+4x^2} \, dx$

Apply substitution

$x=\dfrac{1}{2}\tan u\\ \\dx=\dfrac{1}{2}\cdot \dfrac{1}{\cos ^2 u}du$

Then

$SA=2\pi \int\limits^2_0 x^2\sqrt{1+4x^2} \, dx=2\pi \int\limits^{\arctan(4)}_0 \dfrac{1}{4}\tan^2u\sqrt{1+\tan^2u} \, \dfrac{1}{2}\dfrac{1}{\cos^2u}du=\\ \\=\dfrac{\pi}{4}\int\limits^{\arctan(4)}_0 \tan^2u\sec^3udu=\dfrac{\pi}{4}\int\limits^{\arctan(4)}_0(\sec^3u+\sec^5u)du$

Now

$\int\limits^{\arctan(4)}_0 \sec^3udu=2\sqrt{17}+\dfrac{1}{2}\ln (4+\sqrt{17})\\ \\ \int\limits^{\arctan(4)}_0 \sec^5udu=\dfrac{1}{8}(-(2\sqrt{17}+\dfrac{1}{2}\ln(4+\sqrt{17})))+17\sqrt{17}+\dfrac{3}{4}(2\sqrt{17}+\dfrac{1}{2}\ln (4+\sqrt{17}))$

Hence,

$SA=\pi \dfrac{-\ln(4+\sqrt{17})+132\sqrt{17}}{32}$

3 0

2 years ago

Selina is playing a game that uses the spinner below.

MatroZZZ [7]

Answer:

A) 12.5%

B) 50%

C) 50%

Step-by-step explanation:

For A, 7 is one of the 8 possibilities (1/8). 1/8 of 100 is 12.5, so your chance of spinning a 7 is 12.5%

For B, even numbers are 4/8 or 1/2 of your options. 1/2 of 100 is 50, so your chance of spinning an even number is 50%

For C, there are 4 out of 8 numbers that are prime (2,3,5, & 7).

4/8 or 1/2 of 100 is 50, so your chance of spinning a prime number is 50%

hope this helps

4 0

3 years ago

Name the relationship between the angles below. What is the sum of the angles? Explain how you would find the missing angle. Exp

DiKsa [7]

Answer:

would find the missing angle. Explain each step. (replace with 120 & x)

Name the relationship between the angles below. What is the sum of the angles? Explain how you would find the missing angle. Explain each step. (replace with 120 & x)

Step-by-step explanation:

Name the relationship between the angles below. What is the sum of the angles? Explain how you would find the missing angle. Explain each step. (replace with 120 & x)

8 0

2 years ago

I have attached a picture of the question.

sleet_krkn [62]

Its same i think

100-40=60
130-70=60

8 0

2 years ago

01. En una piscigranja el 30% de boquichicos es el 20% del número de carachamas. Si sólo hay boquichicos y carachamas. ¿Qué porc

Simora [160]

Answer:

0.1. B) 50%

0.2 A) Psicología

Step-by-step explanation:

01. Dejemos que 'x' e 'y' representen el porcentaje de boquichicos y carachamas en la piscifactoría, tenemos;

Dado que el 30% de los boquichicos es el 20% del número de carachamas

30% x = 20% y

∴ 0.3 · x = 0.2 · y

Por lo tanto, tenemos;

x / y = 0,2 / 0,3 = 2/3

Por lo tanto, por cada 100% de pescado, tenemos;

x + y = 100%

x = 2/3 · y

2/3 · y + y = 100%

5 · años / 3 = 100

y = 100 × 3/5 = 60%

El porcentaje de carachamas en la finca, y = 60%

∴ x = 100% - y = 100% - 60% = 40%

El porcentaje de boquichicos en la finca, x = 40%

Por lo tanto, tenemos el 80% del pescado en la granja, obtenemos;

Si hay 100 peces en la granja, 80% = 80 peces

Pero el número de los 100 peces que son boquichicos en la granja = 40% × 100 = 40 peces

Por lo tanto, los boquichicos son la mitad del 80% del número de peces o el 50% de los peces en la piscifactoría.

La opción correcta es;

B) 50%

02. Tenemos;

El costo de un libro de psicología> El costo de un libro en inglés

El costo de un libro de matemáticas> El costo de un libro de historia

El costo de un libro de psicología> El costo de un libro de matemáticas

Por lo tanto, tenemos;

El costo de un libro de psicología> El costo de un libro de matemáticas> El costo de un libro de historia

∴ El libro de Psicología es más caro que todos los demás libros y, por tanto, es el libro más caro

La opción correcta es;

A) Psicología

3 0

2 years ago