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3 years ago

The number 18 is which percent of 15

1 answer:

mihalych1998 [28]3 years ago

4 0

The number 18 is a 120% of the number 15. That is because when you divide the two numbers you get 1.2. Then you multiply this number by a hundred to see what the percentage number is and you get 120 which means that 18 is a 120% of the number 15. Similarly, if you had for example 7, you would divide 7 by 15 and multiply and see that it's just under 50%. This is the basic formula for calculating percentage.

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to estimate the height of the jin mao tower in shanghai , a tourist sights the top of the tower form a mirror that is 86.7 meter

Ray Of Light [21]

Answer:

The height of the tower = 420.48 meters

Step-by-step explanation:

For better understanding of the solution, see the figure attached below :

Let the height of the tower be x meters

Now, using the laws of reflection : angle of reflection = angle of incidence

Also, both the tower and the tourist are standing parallel to each other

⇒ ∠A = ∠i ( Alternate interior angles are equal)

Similarly, ∠D = ∠r ( Alternate interior angles)

But, ∠i = ∠r

⇒ ∠A = ∠D

Also, the tourist and the tower is perpendicular to the ground surface.

⇒ m∠B = m∠E = 90°

Now, in ΔABC and ΔDEC

∠A = ∠D (Proved above)

m∠B = m∠E = 90°

So, by AA postulate of similarity of triangles, ΔABC ~ ΔDEC

As the sides of similar triangles are proportional to each other

$\frac{AB}{DE}=\frac{BC}{EC}\\\\\implies\frac{1.92}{x}=\frac{0.4}{87.6}\\\\\implies x=\frac{87.6\times 1.92}{0.4}\\\\\bf\implies x = 420.48\textbf{ meters}$

Hence, The height of the tower = 420.48 meters

5 0

3 years ago

Roberto decorates retangular signs. One sign is 2/3 foot long and 1/4 foot wide. Another sign is 1/2 long and 1/3 foot wide. It

PilotLPTM [1.2K]

Answer:

It'll take him 1/4 hours to decorate the two signs.

Step-by-step explanation:

In order to know how long Roberto will take to decorate all the signs we need to find their surface area, since they're rectangular their area is given by the product of their dimensions.

First sign:

area1 = (2/3)*(1/4) = 2/12 = 1/6 foot²

Second sign:

area2 = (1/2)*(1/3) = 1/6 foot²

The total area he has to paint is the sum of their individual areas, so we have:

total area = area1 + area2 = 1/6 + 1/6 = 2/6 = 1/3 foot²

To find out how long he'll take to decorate this area we can use a rule of three as shown bellow:

3/4 hour -> 1 foot²

x hour -> 1/3 foot²

x = (3/4)*(1/3) = 1/4 hours

3 0

3 years ago

Write the equation of a line perpendicular to 9xplus7yequals6 that passes through the point (9,negative 7).

andrew11 [14]

$k:\ y=m_1x+b_1\\\\l:\ y=m_2x+b_2\\\\k\ ||\ l\iff m_1=m_2\\\\k\ \perp\ l\iff m_1m_2=-1$

We have:

$k:\ 9x+7y=6\ \ \ |-9x\\\\7y=-9x+6\ \ \ \ |:7\\\\y=-\dfrac{9}{7}x+\dfrac{6}{9}\to m_1=-\dfrac{9}{7}\\\\l:\ y=m_2x+b\\\\l\ \perp\ k\iff-\dfrac{9}{7}m_2=-1\ \ \ \ |\cdot\left(-\dfrac{7}{9}\right)\\\\m_2=\dfrac{7}{9}\to\ l:\ y=\dfrac{7}{9}x+b$