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3 years ago

10 pens cost £4.00 find the cost of 7 pens

2 answers:

5 0

The answer is £2.80. To find the cost of 1 pen, you divide £4 (all 10 pens) by 10 which gives you 40p. To find 7 pens, you multiply 40p (1 pen) by 7. £0.40 x 7 = £2.80

Nina [5.8K]3 years ago

3 0

Well, the first thing we need to do is divide 10 by 4. These teo numbers are the number of pens, and cost of them. So,
================================
10 / 4 = 2.5
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Now we have to use the answer we got, 2.5 which is the cost of 1 pen, and multiply it by 7.
================================
2.5 x 7 = 17.5
--------------------------------------------------------
This means that 7 pens cost <span>£</span>17.5

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Change each of the following points from rectangular coordinates to spherical coordinates and to cylindrical coordinates.

FromTheMoon [43]

Answer and Step-by-step explanation: Spherical coordinate describes a location of a point in space: one distance (ρ) and two angles (Ф,θ).To transform cartesian coordinates into spherical coordinates:

$\rho = \sqrt{x^{2}+y^{2}+z^{2}}$

$\phi = cos^{-1}\frac{z}{\rho}$

For angle θ:

If x > 0 and y > 0: $\theta = tan^{-1}\frac{y}{x}$ ;

If x < 0: $\theta = \pi + tan^{-1}\frac{y}{x}$ ;
If x > 0 and y < 0: $\theta = 2\pi + tan^{-1}\frac{y}{x}$ ;

Calculating:

a) (4,2,-4)

$\rho = \sqrt{4^{2}+2^{2}+(-4)^{2}}$ = 6

$\phi = cos^{-1}(\frac{-4}{6})$

$\phi = cos^{-1}(\frac{-2}{3})$

For θ, choose 1st option:

$\theta = tan^{-1}(\frac{2}{4})$

$\theta = tan^{-1}(\frac{1}{2})$

b) (0,8,15)

$\rho = \sqrt{0^{2}+8^{2}+(15)^{2}}$ = 17

$\phi = cos^{-1}(\frac{15}{17})$

$\theta = tan^{-1}\frac{y}{x}$

The angle θ gives a tangent that doesn't exist. Analysing table of sine, cosine and tangent: θ = $\frac{\pi}{2}$

c) (√2,1,1)

$\rho = \sqrt{(\sqrt{2} )^{2}+1^{2}+1^{2}}$ = 2

$\phi = cos^{-1}(\frac{1}{2})$

$\phi$ = $\frac{\pi}{3}$

$\theta = tan^{-1}\frac{1}{\sqrt{2} }$

d) (−2√3,−2,3)

$\rho = \sqrt{(-2\sqrt{3} )^{2}+(-2)^{2}+3^{2}}$ = 5

$\phi = cos^{-1}(\frac{3}{5})$

Since x < 0, use 2nd option:

$\theta = \pi + tan^{-1}\frac{1}{\sqrt{3} }$

$\theta = \pi + \frac{\pi}{6}$

$\theta = \frac{7\pi}{6}$

Cilindrical coordinate describes a 3 dimension space: 2 distances (r and z) and 1 angle (θ). To express cartesian coordinates into cilindrical:

$r=\sqrt{x^{2}+y^{2}}$

Angle θ is the same as spherical coordinate;

z = z

Calculating:

a) (4,2,-4)

$r=\sqrt{4^{2}+2^{2}}$ = $\sqrt{20}$

$\theta = tan^{-1}\frac{1}{2}$

z = -4

b) (0, 8, 15)

$r=\sqrt{0^{2}+8^{2}}$ = 8

$\theta = \frac{\pi}{2}$

z = 15

c) (√2,1,1)

$r=\sqrt{(\sqrt{2} )^{2}+1^{2}}$ = $\sqrt{3}$

$\theta = \frac{\pi}{3}$

z = 1

d) (−2√3,−2,3)

$r=\sqrt{(-2\sqrt{3} )^{2}+(-2)^{2}}$ = 4

$\theta = \frac{7\pi}{6}$

z = 3

5 0

3 years ago

What is the difference between a relation and function? Classify each of the following as a function, or not a function. State t

Levart [38]

Answer:

A relation is a subset of cartesian product of two non empty sets whereas A function is a type of relation in which every element of first set has one and only image in the second set.

In a relation an element of the first set can have many images in the second set whereas in a function the first element can have only one image in the second set.

The given relation is not a function as the element 1 is related to 3 different elements in the second set.

Domain={1}

Range={7,14,21}

5 0

2 years ago

Find the opposite of -16

ryzh [129]

Answer:

please give me brainlest

Step-by-step explanation:

16 is the answers for the question

5 0

2 years ago

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What is a decimal ( Definition, Example, Non-Example, Facts/Characteristics)

evablogger [386]

A decimal is "." this symbol is used to separate whole numbers from a number value that is less than 1. Decimals basically puts things in its correct "place" according to the place value chart. | Example : $ 1.70 ; Without the decimal point this would be 170$ and in reality it is only one dollar and seventy cents. |

5 0

4 years ago

Simplify. (Assume all variables represent positive real numbers). Leave answer in radical form.

Flauer [41]

Answer:

$\sqrt{128a^{6}b^{13}} = 8 a^{3} b^{6} \sqrt{2b}$