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Mathematics 15 Online
OpenStudy (anonymous):

I need helping finding Figure A,B,C,D,E pleassee

OpenStudy (anonymous):

ignore the top question (that answer is 1170 btw) just look at the figures

OpenStudy (anonymous):

@Michele_Laino

OpenStudy (michele_laino):

here, we have a geometric shape, which is composed by a rectangle and two trapezoids. Now the area of the rectangle is \(35 \cdot 18=...?\)

OpenStudy (anonymous):

630

OpenStudy (michele_laino):

correct!

OpenStudy (michele_laino):

the area of one trapezoid is \(base \times height= 18 \cdot 15=...?\)

OpenStudy (anonymous):

270

OpenStudy (michele_laino):

correct! So total area of the geometric shape is: \(270+270+630=...?\)

OpenStudy (anonymous):

1170

OpenStudy (michele_laino):

correct!

OpenStudy (anonymous):

okay since that part is done how do we do the figures a b c d and e

OpenStudy (michele_laino):

sorry!, I go on parts a, b, c, d, e

OpenStudy (anonymous):

huh?

OpenStudy (michele_laino):

if the perimeter of the rombus is \(20\) then each of its side measures \(20/4=...?\)

OpenStudy (anonymous):

5

OpenStudy (michele_laino):

correct!

OpenStudy (anonymous):

is that the answer or is there more to it?

OpenStudy (michele_laino):

no, we have to do more computations. Now the situation is like below:

OpenStudy (anonymous):

okay

OpenStudy (michele_laino):

|dw:1446145080906:dw|

OpenStudy (anonymous):

ok

OpenStudy (michele_laino):

since the lenght of diagonal is \(8\) then the length of half diagonal is \(4\), and the length of the other half diagonal is \(x\) we have to establish what is the value of \(x\)

OpenStudy (anonymous):

yeah

OpenStudy (michele_laino):

If we apply the theorem of Pitagora, I can write this: \[x = \sqrt {{5^2} - {4^2}} = \sqrt {25 - 16} = ...?\]

OpenStudy (anonymous):

-11?

OpenStudy (michele_laino):

we have \(25-16=9\), so what is square root of \(9\)?

OpenStudy (anonymous):

3

OpenStudy (michele_laino):

correct! so the length of second diagonal is: \(3 \cdot 2=6\)

OpenStudy (anonymous):

alright

OpenStudy (michele_laino):

Now, the area \(A\) of the rombus is given by the subsequent formula: \[\Large A = \frac{{{d_1}{d_2}}}{2} = \frac{{8 \cdot 6}}{2} = ...?\]

OpenStudy (anonymous):

24

OpenStudy (michele_laino):

that's right!

OpenStudy (anonymous):

is that the answer ?

OpenStudy (michele_laino):

yes! Please write the right unit of measure, so we have: \(A=24\,m^2\) now I go to solve part B.

OpenStudy (anonymous):

okay great

OpenStudy (michele_laino):

here we can find the length of each side of the rombus, so we get: \[\Large side = \frac{{perimeter}}{4} = \frac{{52}}{4} = ...?\]

OpenStudy (anonymous):

13

OpenStudy (michele_laino):

correct!

OpenStudy (michele_laino):

now we have this situation: |dw:1446145743159:dw| since the lenght of half diagonal is \(24/2=12\)

OpenStudy (anonymous):

okay

OpenStudy (michele_laino):

again, I apply the theorem of Pitagora, in order to establish the value of the second half diagonal \(x\), so I can write: \[\Large x = \sqrt {{{13}^2} - {{12}^2}} = \sqrt {169 - 144} = ...?\]

OpenStudy (anonymous):

131

OpenStudy (michele_laino):

hint: we have: \(169-144=25\), so what is the square root of \(25\)?

OpenStudy (anonymous):

5

OpenStudy (michele_laino):

correct! So the length of second diagonal is: \(5 \cdot 2=10\)

OpenStudy (michele_laino):

Again I compute the area \(A\) of the rombus like below: \[\Large A = \frac{{{d_1}{d_2}}}{2} = \frac{{24 \cdot 10}}{2} = ...?\]

OpenStudy (anonymous):

120

OpenStudy (michele_laino):

that's right!

OpenStudy (michele_laino):

more precisely we have \(A=120\,m^2\)

OpenStudy (anonymous):

yay ok

OpenStudy (michele_laino):

Now, I solve part C.

OpenStudy (anonymous):

mhm

OpenStudy (michele_laino):

here we have an equilateral triangle, and the length of each side is \(15\,m\) here is the corresponding drawing: |dw:1446146329233:dw|

OpenStudy (anonymous):

oh okay

OpenStudy (michele_laino):

CH is the height of the equilateral triangle with respect to the base AB, so, we can write: \[BH = \frac{{AB}}{2} = \frac{{15}}{2} = 7.5\]

OpenStudy (anonymous):

oh okay os BH and CH are the same

OpenStudy (michele_laino):

No, please CH is different from BH |dw:1446146505064:dw| Now I apply the theorem of Pitagora, so, I can write: \[\Large x = \sqrt {{{15}^2} - {{7.5}^2}} = \sqrt {225 - 56.25} = ...?\]

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