CD is a ⊥ dropped from C. If the area of ∆ADC

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CD is a ⊥ dropped from C. If the area of ∆ADC is ‘a’, then the area of D BDC is :

1. (30 – a) sq. units
2. (60 – a) sq. units
3. a + 12 a sq. units
  5
4. None of these

Correct Option: A

5² + 12² = 13²
∆ABC is a right angled triangle.
∆ADC + ∆BDC = ∆ABC

⇒ a + ∆BDC =	1	× 5 × 12 = 30
	2

⇒ ∆BDC = (30 – a) sq. units.