A 1.5 m tall boy is standing at some distance from a 30 m tall b

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 Multiple Choice QuestionsShort Answer Type

1.

A circus artist is climbing a 20 m long rope, which is tightly stretched and tied from the top of a vertical pole to the ground. Find the height of the pole, if the angle made by the rope with the ground level is 30° (see Fig. 9.11)


Fig. 9.11

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2.

A tree breaks due to storm and the broken part bends so that the top of the tree touches the ground making an angle 30° with it. The distance between the foot of the tree to the point where the top touches the ground is 8 m. Find the height of the tree. 

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3.

A contractor plans to install two slides for the children to play in a park. For the children below the age of 5 years, she prefers to have a slide whose top is at a height of 1.5 m, and is inclined at an angle of 30° to the ground, whereas for elder children, she wants to have a steep slide at a height of 3m, and inclined at an angle of 60° to the ground. What should be the length of the slide in each case? 

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4.

The angle of elevation of the top of a tower from a point on the ground, which is 30 m away from the foot of the tower, is 30°. Find the height of the tower.

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5.

A kite is flying at a height of 60 m above the ground. The string attached to the kite is temporarily tied to a point on the ground. The inclination of the string with the ground is 60°. Find the length of the string, assuming that there is no slack in the string.

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 Multiple Choice QuestionsLong Answer Type

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6. A 1.5 m tall boy is standing at some distance from a 30 m tall building. The angle of elevation from his eyes to the top of the building increases from 30° from 60°, as he walks towards the building. Find the distance he walked towards the building.


Let AC be the observer of height 1.5 m and BE be the building of height 30 m. The angle of elevation from the eyes of observer increases from 30° to 60° to the top of the building.


Let AC be the observer of height 1.5 m and BE be the building of heig

Fig. 9.8.

i.e.,    ∠ECD = 30° and ∠EFD = 60°.
Let CF = x m and FD = y m
In right triangle EDF, we have

tan space 60 degree space equals space DE over DF space open square brackets table row cell DE space equals space BE minus BD end cell row cell equals 30 minus 1.5 end cell row cell equals 28.5 space straight m end cell end table close square brackets
rightwards double arrow space space space space space square root of 3 equals fraction numerator 28.5 over denominator straight y end fraction
rightwards double arrow space space space space space space straight y space equals space fraction numerator 28.5 over denominator square root of 3 end fraction equals fraction numerator 28.5 square root of 3 over denominator 3 end fraction space space space space... left parenthesis straight i right parenthesis
In right triangle EDC, we have

tan space 30 degree space space equals space space DE over DC
space space space fraction numerator 1 over denominator square root of 3 end fraction space equals space fraction numerator 28.5 over denominator DF plus CF end fraction
rightwards double arrow space space fraction numerator 1 over denominator square root of 3 end fraction space equals space fraction numerator 28.5 over denominator straight y plus straight x end fraction
rightwards double arrow space space straight x plus straight y equals 28.5 square root of 3
rightwards double arrow space space space space space straight y space equals space 28.5 square root of 3 minus straight x space space space space space... left parenthesis ii right parenthesis
Comparing (i) and (ii), we get

fraction numerator 28.5 square root of 3 over denominator 3 end fraction space equals space 28.5 square root of 3 space minus straight x
rightwards double arrow space space straight x space equals space 28.5 square root of 3 minus fraction numerator 28.5 square root of 3 over denominator 3 end fraction
equals space fraction numerator 3 left parenthesis 28.5 square root of 3 right parenthesis minus 28.5 square root of 3 space over denominator 2 end fraction space equals fraction numerator 85.5 square root of 3 minus 28.5 square root of 3 over denominator 3 end fraction
equals fraction numerator 57 square root of 3 over denominator 3 end fraction equals 19 square root of 3 space straight m
Hence, distance (CF) equals space 19 square root of 3 space straight m

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 Multiple Choice QuestionsShort Answer Type

7.

From a point on the ground, the angles of elevation of the bottom and the top of a transmission tower fixed at the top of a 20 m high building are 45° and 60° respectively. Find the height of the tower.

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 Multiple Choice QuestionsLong Answer Type

8.

A statue, 1.6 m tall, stands on the top of a pedestal. From a point on the ground, the angle of elevation of the top of the statue is 60° and from the same point the angle of elevation of the top of the pedestal is 45°. Find the height of the pedestal.

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9.

The angle of elevation of the top of a building from the foot of the tower is 30° and the angle of elevation of the top of the tower from the foot of the building is 60°. If the tower is 50 m high, find the height of the building.

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 Multiple Choice QuestionsShort Answer Type

10.

Two poles of equal heights are standing opposite each other on either side of the road, which is 80 m wide. From a point between them on the road, the angles of elevation of the top of the poles are 60° and 30°, respectively. Find the height of the poles and the distances of the point from the poles.

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