Q9 of 45 Page 138

A ladder on the platform of a fire brigade van can be elevated at an angle of 70° to the maximum. The length of the ladder can be extended upto 20m. If the platform is 2m above the ground, find the maximum height from the ground upto which the ladder can reach. (sin 70° = 0.94)


Let AB be the ladder, i.e. AB = 20 m and PQRS be the platform.


In the above figure, clearly


PQ = RS = CD = height of platform = 2 m


Maximum height ladder can reach = BC + CD


Now,


Maximum value of ∠BAC = 70°


In right-angled triangle ABC,





⇒ BC = 18.8 m


Maximum height ladder can reach = BC + CD


= 18.8 + 2 = 20.8 meters


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