Ruhhr
the figures are similar. The area of one figure is given. Find the area of the other figure to the nearest whole number. The area of the large triangle is 177 ft²
(will draw figure below) ..
A) 100 ft² .. B) 347 ft² .. C) 196 ft² .. D) 90 ft²
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Ruhhr
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|dw:1349190507668:dw|
(not drawn to scale)
pratu043
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What is 14 ft and 10 ft?
pratu043
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|dw:1349190940501:dw|
pratu043
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Are you there @Ruhhr?
pratu043
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?????
Ruhhr
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Sorry, getting caught up in my work.. & yeah it shows the lenght of the sides... I got that already..
pratu043
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I'm not really good at this but the ration of the sides are the same right?
pratu043
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Sorry ratio.
pratu043
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|dw:1349191230318:dw|
Ruhhr
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Ratio: is a comparison of two quantities by division.
pratu043
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So 14:10 = AB:PQ = BC:QR
pratu043
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14:10 = 7:5
Ruhhr
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How does it equal 7.5 though? What did you do to get to 7.5?
pratu043
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No not 7.5 its 7:5.
If you divide 14:10 by two, you get 7:5(14/2:10/2).
Got that?
Ruhhr
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Oh yes! Got it!
Then what do you do?
pratu043
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Area of ABC = 177 ft^2
Lets take the base as 14 ft so that we can find the altitude to that base. You need the altitude and the corresponding base to get the area.
1/2 * base * height = 177
1/2 * 14 * h = 177
h = (177 * 2)14
= 25.3 approx. (25.28)
pratu043
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Pretty straightforward now.
pratu043
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Got it till here?
Ruhhr
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wait how did you get 177 when all it provides is 14?
pratu043
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The area is 177 right? Its given.
pratu043
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Area of the largest triangle is 177 ft^2.
pratu043
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sorry larger. Got that?
Ruhhr
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yes
pratu043
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So even the heights of the two triangles are in the ratio of 7:5.
So lets take the height to the base 10 ft in PQR as x.
25.3:x = 7:5
=> 25.3/x = 7/5
Can you find x?
Ruhhr
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I'm lost @.@
pratu043
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Lost on how to find x?
Ruhhr
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yes
pratu043
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Hint - In the equation 25.3/x = 7/5, cross multiply.
You'll get 25.3 * 5 = 7x.
Now?
Ruhhr
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I get 7x = 127.5 by cross multiplying
Ruhhr
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I get 7x = 127.5 by cross multiplying
pratu043
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So what's x?
Ruhhr
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and when i divide that.. i get 18.21
Ruhhr
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igtg to my next class now
pratu043
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Yep that's right.
So now we have the corresponding base and height for PQR.
1/2 * 18.21 * 10
Easy now?
pratu043
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You get 91.05. I think you should round off to the nearest ten and write it as 90.