- 30
- 60
- 20
- 40

Option 4 : 40

**Given:**

The height of the tower 100 m

**Concept:**

tanθ = (Perpendicular)/(Base)

**Calculation:**

Let be assume speed of car is S.

⇒ Angle of depression = Angle of elevation

⇒ In ΔABC, tan30° = 100/(x + 10S)

⇒ 1/√3 = 100/(x + 10S) ... (1)

⇒ In ΔABD, tan60° = 100/x

⇒ √3 = 100/x .... (2)

⇒ From equation (1) and (2)

⇒ S = 20/√3 m/s or (20/√3) × (18/5) ≈ 40 km/h

**∴ The required result will be 40 km/h.**

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