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In an isosceles triangle, altitude is a perpendicular bisector of the base.
Thus, \(w^2 + 9^2 = 15^2\)
\(w^2 = 225 - 81\)
\(w = \sqrt{144} = 12\) (Choice B)
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Bunuel

The figure above shows a row of triangular tiles each with two sides 15 centimeters long and one side 18 centimeters long. What is w, the width of the row, in centimeters?

(A) 10
(B) 12
(C) 15
(D) 9√2
(E) 9√3


Attachment:
2017-08-09_1258.png
Each triangle contains a 3-4-5 right triangle.

Width of row = altitude of one triangle.

Altitude of the isosceles triangle is a perpendicular bisector of the base; intercept point creates two right angles and divides base in half.

Base = 9. Hypotenuse = 15. Multiple of 3, and . . . Multiple of 5 . . .

If 3-4-5 right triangle is familiar, no need to calculate; 9-12-15 is common.

Answer B
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