If each of the line segments in the figure above has a length equal to 4, and the angles a, b and c are each 60 degrees, what is the total area of the shaded figures?
A) 16
B) 8sqrt3
C) 24sqrt2
D) 36
E) 24sqrt3
Answer is 24sqrt3
Coordinate Geometry
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If each line segment in the figure is equal to 4, we're looking for the area of 3 equal RHOMBUSES (rhombi? No one knows).
(Forgive the crude rendering... geometry is always the hardest to explain digitally!)
If the angles a, b, and c are all 60, then the opposite angles are 60, and the other angles 120:
This means that we can chop each rhombus into 2 identical EQUILATERAL triangles. (Btw, the 60-120-60-120 rhombus is the most common form of a rhombus on the GMAT).
Now, we can simply calculate the area of a single equilateral triangle, then multiply by 6.
AREA OF EQUILATERAL: remember that you can chop an equilateral triangle into two 30-60-90 right triangles. You should have the ratio for these memorized:
Thus, the base of each triangle is 4, and the height is 2(sqrt3). So (1/2)bh = 4(sqrt3)
Since we have 6 such equilateral triangles, the total area = (6)(4(sqrt3)) = 24(sqrt3)
The answer is E.
(Forgive the crude rendering... geometry is always the hardest to explain digitally!)
If the angles a, b, and c are all 60, then the opposite angles are 60, and the other angles 120:
This means that we can chop each rhombus into 2 identical EQUILATERAL triangles. (Btw, the 60-120-60-120 rhombus is the most common form of a rhombus on the GMAT).
Now, we can simply calculate the area of a single equilateral triangle, then multiply by 6.
AREA OF EQUILATERAL: remember that you can chop an equilateral triangle into two 30-60-90 right triangles. You should have the ratio for these memorized:
Thus, the base of each triangle is 4, and the height is 2(sqrt3). So (1/2)bh = 4(sqrt3)
Since we have 6 such equilateral triangles, the total area = (6)(4(sqrt3)) = 24(sqrt3)
The answer is E.
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
GMAT/MBA Expert
- ceilidh.erickson
- GMAT Instructor
- Posts: 2095
- Joined: Tue Dec 04, 2012 3:22 pm
- Thanked: 1443 times
- Followed by:247 members
For a somewhat similar area-of-rhombus question, see example #2 in this article: https://www.manhattanprep.com/gmat/blog ... ncy-wrong/
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
EdM in Mind, Brain, and Education
Harvard Graduate School of Education