MathBrush

Triangular blocks — Mr Kumar's workbench

Mr Kumar stands three identical equilateral triangular wooden blocks, Block A, Block B and Block C, upright in a straight groove on his workbench. Each block rests with its bottom edge lying flat along the groove. Block A is on the left, Block B is in the middle and Block C is on the right. Block B overlaps Block A when seen from the front, and Block B also overlaps Block C, but Block A and Block C do not overlap each other. Measured along the groove: • the distance from the left corner of Block A to the left corner of Block B is 25 cm, • the distance from the left corner of Block C to the right corner of Block B is 5 cm, • the distance from the right corner of Block A to the right corner of Block C is 52 cm. The shaded parts are the part of Block A that is not hidden by Block B, and the part of Block C that is not hidden by Block B. (a) Find the length of one side of a block. (b) Find the total perimeter of the two shaded parts.

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