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Two similar triangular glass panes are cut from the same sheet, so the cost of a pane is proportional to its area. The larger pane has perimeter 63 cm and the smaller has perimeter 49 cm, and the larger pane costs Rs 810.
Find the cost of the smaller pane (in Rs).

Class 10Areas of Similar TrianglesGeometry — Similarity
  • A630
  • B1041.4
  • C490
  • D405

Step-by-Step Solution

Perimeter ratio smaller : larger = 49 : 63 = 7 : 9, so the area ratio, and therefore the cost ratio, is . Smaller cost = = Rs 490. Using the perimeter ratio without squaring gives Rs 630, scaling the wrong way by gives about Rs 1041.4, and Rs 405 is simply half of 810.
Answer: C) 490

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