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3 years ago

The two shapes have the same area. Work out the perimeter of the rectangle.

Mathematics

1 answer:

elena-14-01-66 [18.8K]3 years ago

4 0

You need to do this in several steps.

1) Using the given length and width of the rectangle, find its area.
2) Then using the base and height of the triangle, find its area.
3) Since the areas are equal, set the expressions equal to each other, and solve for x.
4) Using the value of x you found, find the length and width of the rectangle and find its perimeter.

1) The area of the rectangle is A = LW
Area of Rectangle = (x + 2)x = x^2 + 2x

2) The area of the triangle is A = (1/2)bh
Area of Triangle = (1/2)(24)x = 12x

3) Set the areas equal and solve for x

x^2 + 2x = 12x

x^2 - 10x = 0

x(x - 10) = 0

x = 0 or x = 10

Since a width cannot be 0, we discard x = 0, and keep x = 10.

4) The length is x + 2 = 10 + 2 = 12
The width is x = 10

The perimeter is 2(L + W) = 2(10 + 2) = 2(22) = 44

The perimeter is 44 cm.

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If a,b,c and d are positive real numbers such that logab=8/9, logbc=-3/4, logcd=2, find the value of logd(abc)

Eva8 [605]

We can expand the logarithm of a product as a sum of logarithms:

$\log_dabc=\log_da+\log_db+\log_dc$

Then using the change of base formula, we can derive the relationship

$\log_xy=\dfrac{\ln y}{\ln x}=\dfrac1{\frac{\ln x}{\ln y}}=\dfrac1{\log_yx}$

This immediately tells us that

$\log_dc=\dfrac1{\log_cd}=\dfrac12$

Notice that none of $a,b,c,d$ can be equal to 1. This is because

$\log_1x=y\implies1^{\log_1x}=1^y\implies x=1$

for any choice of $y$ . This means we can safely do the following without worrying about division by 0.

$\log_db=\dfrac{\ln b}{\ln d}=\dfrac{\frac{\ln b}{\ln c}}{\frac{\ln d}{\ln c}}=\dfrac{\log_cb}{\log_cd}=\dfrac1{\log_bc\log_cd}$

so that

$\log_db=\dfrac1{-\frac34\cdot2}=-\dfrac23$

Similarly,

$\log_da=\dfrac{\ln a}{\ln d}=\dfrac{\frac{\ln a}{\ln b}}{\frac{\ln d}{\ln b}}=\dfrac{\log_ba}{\log_bd}=\dfrac{\log_db}{\log_ab}$

so that

$\log_da=\dfrac{-\frac23}{\frac89}=-\dfrac34$

So we end up with

$\log_dabc=-\dfrac34-\dfrac23+\dfrac12=-\dfrac{11}{12}$

###

Another way to do this:

$\log_ab=\dfrac89\implies a^{8/9}=b\implies a=b^{9/8}$

$\log_bc=-\dfrac34\implies b^{-3/4}=c\implies b=c^{-4/3}$

$\log_cd=2\implies c^2=d\implies\log_dc^2=1\implies\log_dc=\dfrac12$

Then

$abc=(c^{-4/3})^{9/8}c^{-4/3}c=c^{-11/6}$

So we have

$\log_dabc=\log_dc^{-11/6}=-\dfrac{11}6\log_dc=-\dfrac{11}6\cdot\dfrac12=-\dfrac{11}{12}$

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3 years ago

How many gallons of pure alcohol should be added to 40 gallons of a 20% solution so

Rudik [331]

Answer:

8/3

Step-by-step explanation:

i put equations as this:

x+40 = y

where x is galllons of pure mixture and y is the gallons of the new mixture

the other equation i id was:

x+0.2(40) = 0.25y

x+8 = 0.25y

y = 4x+32

solve using substitution

(x+40) = 4x+32

x = 4x-8

-3x = -8

x = 8/3

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3 years ago

Determine whether a triangle can be formed with the given side lengths. If the side lengths

scoundrel [369]

Answer:

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3 years ago

Read each problem and decide what operation you

Vlada [557]

Answer:

b = 3.5 cm

Step-by-step explanation:

Given that,

The area of a rectangle, A = 14. sq cm

The length of one side, l = 4 cm

We need to find the length of another side. The formula for the area of a rectangle is given by :

A = lb

So,

$14=4b\\\\b=\dfrac{14}{4}\\\\b=3.5\ cm$

So, the length of the other side is equal to 3.5 cm.

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3 years ago

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Answer:

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