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Two vertical poles are on either side of a road. A 30 m long ladder is placed between the two poles. When the ladder rests against one pole, it makes angle 32° 24' with the pole and when it is turned to rest against another pole, it makes angle 32° 24' with the road. Calculate the width of the road.

Heights & Distances

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Answer

Let AP and CQ be two poles.

Two vertical poles are on either side of a road. A 30 m long ladder is placed between the two poles. When the ladder rests against one pole, it makes angle 32° 24' with the pole and when it is turned to rest against another pole, it makes angle 32° 24' with the road. Calculate the width of the road. Heights and Distances, Concise Mathematics Solutions ICSE Class 10.

When ladder is at position AB resting on pole AP.

Then, ∠BAP = 32° 24'

From figure,

In △ABP,

sin 32° 24=PerpendicularHypotenuse0.536=BPABBP=AB×0.536BP=30×0.536BP=16.08 meters.\text{sin 32° 24}' = \dfrac{\text{Perpendicular}}{\text{Hypotenuse}} \\[1em] \Rightarrow 0.536 = \dfrac{BP}{AB} \\[1em] \Rightarrow BP = AB \times 0.536 \\[1em] \Rightarrow BP = 30 \times 0.536 \\[1em] \Rightarrow BP = 16.08 \text{ meters}.

When ladder is at position BC resting on pole CQ.

Then it makes angle 32° 24' with road.

∴ ∠CBQ = 32° 24'

From figure,

In △BQC,

cos 32° 24=BaseHypotenuse0.844=BQBCBQ=BC×0.844BQ=30×0.844BQ=25.32 meters.\text{cos 32° 24}' = \dfrac{\text{Base}}{\text{Hypotenuse}} \\[1em] \Rightarrow 0.844 = \dfrac{BQ}{BC} \\[1em] \Rightarrow BQ = BC \times 0.844 \\[1em] \Rightarrow BQ = 30 \times 0.844 \\[1em] \Rightarrow BQ = 25.32\text{ meters}.

Width of road = BP + BQ = 16.08 + 25.32 = 41.4 meters.

Hence, width of road = 41.4 meters.

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