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ECE Board November 1998: Two triangles have equal bases. The altitude of one triangle is 3 units more than its base and the altitude of the other triangle is 3 units less than its base. Find the altitudes, if the areas of the triangles differ by 21 square units.

  1. 6 and 12
  2. 3 and 9
  3. 5 and 11
  4. 4 and 10

Answer

D. 4 and 10

Solution

Let b be the common base. Areas: A1= 12b(b+3), A2= 12b(b-3). A1-A2= 12b(6)=3b=21 b=7. The altitudes are b+3=10 and b-3=4.

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