Ejeje J.

asked • 07/24/25

Find the perimeter and surface area

https://ibb.co/Jj8jM5gX

Doug C.

This is a poorly constructed problem, because the diagram assumes the triangle in the top left is equilateral. It does not have to be. The area does not change if the top vertex is moved slightly off center, but the perimeter does. Drag point C on this graph to see that the triangle area does not change, but its perimeter does: desmos.com/calculator/945ncuu6cw
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07/24/25

Christina P.

tutor
It cannot be equilateral, because its base is 4 and its height is 4. I assume that they intend for it to be isosceles, making the legs 2*sqrt5, but we know what assuming does! ;)
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07/25/25

Doug C.

Yes, I meant isosceles.
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07/25/25

1 Expert Answer

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JACQUES D. answered • 07/25/25

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Let's call the parts, small triangle, small ,l medium, and large rectangles.


Triangle: has dimensions of 4 base, 4 height (isosceles, so sides are sqrt(2^2+4^2) = 2sqrt(5))

Perimeter = 2(2sqrt(5) Area = 1/2(4*4) = 8


Small rectangle: Perimeter = 2*4+5 Area = 4*5

Medium Rectangle Perimeter = 2*12 Area = 4*12

Large Rectangle Perimeter = 2*(6+15) - (5+4) Area = 6*15


Hope that helps. Please consider a tutor!

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Doug C.

Although the triangle looks isosceles, the diagram gives no indication that it actually is.
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07/25/25

Brenda D.

tutor
Agreed and with the first set of comments, I would suggest that the requester, Ejeje J. confirm whether or not the assumption is valid. Maybe the applicability of the assumption itself is the true question being asked about the diagram.
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07/29/25

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