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February 6th, 2019, 05:53 PM   #1
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triangle?

Could not solve this on my exam.

Please help with explanation.

Thanks.

Find the value of x which makes the area of this triangle equal 72.
A. x=10.5
B. x=6
C. x=4.6875
D. x=9.375
triangle


Last edited by skipjack; February 6th, 2019 at 09:28 PM.
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February 6th, 2019, 07:38 PM   #2
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A=(1/2)(b)(h)

72=(1/2)(8)(h)
[do keep in mind that h=(2x-3)]

72=(4)(h)

18=h

Therefore, if h=18 and h=(2x-3) then 18=2x-3

18=2x-3

21=2x

10.5=x


Final answer: A
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February 6th, 2019, 09:43 PM   #3
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The triangle can be thought of as the lower left half of a rectangle (with area 72 × 2 = 144).
The height of that rectangle (and also the triangle) is therefore 144/8 = 18.
Hence 2x - 3 = 18, which implies that x = 10.5 (answer A).

I've no idea how anyone could arrive at answer C or D.
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