In a right-angled triangle ABC, AB=15 cm, BC=20 cm and AC=25 cm. Further, BP is the perpendicular on AC. What is the difference in the area of triangles PAB and PCB?

  1. A. 40 square cm
  2. B. 42 square cm
  3. C. 45 square cm
  4. D. 48 square cm

Correct Answer: B. 42 square cm

Explanation

In right \Delta ABC, BP = \frac{AB \times BC}{AC} = \frac{15 \times 20}{25} = 12 cm. Also, AP = \frac{AB^2}{AC} = 9 cm and PC = \frac{BC^2}{AC} = 16 cm. The difference in their bases is 16 - 9 = 7 cm. The difference in area is \frac{1}{2} \times \text{base\_diff} \times \text{height} = \frac{1}{2} \times 7 \times 12 = 42 sq cm.

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