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Answer:
B. a = 10√3, b = 5√3, c = 15, d = 5
Explanation:
When you examine the angles of these triangles, you see that all of the triangles are 30°-60°-90° triangles, so ratios of corresponding sides are the same.
Examining the answer choices, you see that all of them agree that ...
a = 10√3, c = 15
Since b is the long leg of the smallest triangle, you know that b > d. This is only the case in answer choices B and D.
The leg marked 'a' is the long leg of the largest triangle, whose short leg is 10. That is the ratio of the longer to shorter legs is 10√3 : 10 = √3 : 1. The ratio of 'b' to 'd' needs to be the same, matching only answer choice B.
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The ratios of the sides of a 30-60-90 triangle are 1 : √3 : 2. This tells you that ...
d = 10/2 = 5
c+d = 10×2 = 20 ⇒ c = 20 -5 = 15
b = 5√3
a = 10√3
As a check, c = b×√3 = (5√3)(√3) = 5·3 = 15. (matches above)