129 m from the foot of a cliff on level of ground, the angle of elevation of the top of a cliff is . The height of this cliff is

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C.

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A 25m long ladder is rested on a wall. The foot of the ladder is 7m away from the wall. If the end of the ladder (resting on the wall) slides down 4m, then how far will its foot move away?

• 5 m

• 8 m

• 9 m

• 10 m

B.

8 m

In , 

   
So, the height of ladder from ground  = 24 m
When, the end of the ladder slides down 4 m, then
The height of ladder from ground = 24 - 4 = 20 m
In 

 The foot of ladder will move away = 15 - 7 = 8 m
                

A man on the top of a tower, standing on the sea shore, finds that a boat coming towards him takes 10 minutes for the angle of depression to change from 30° to 60°. How soon the boat reach the sea-shore?

• 5 minutes

• 7 minutes

• 10 minutes

• 15 minutes

A.

5 minutes

Let speed of boat  = v metre/minute
Time taken to reach B from D = t minutes
 [given]
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A man standing on the bank of a river observes that the angle of elevation of the top of a tree just on the opposite bank is 60°. But the angle of elevation is 30° from a point which is at a distance of  from the bank. Then the height of the tree

• 60 ft

• 45 ft

• 30 ft

• 15 ft

C.

30 ft

Let the height of the tree be h ft
In ΔBDC,

 
In ABC,

A man standing on the bank of river observes that the angle subtended by a tree on the opposite bank is . When he retires 36 m from the bank, he finds that the angle is 30o. The breadth of the river is

• 15 m

• 18 m

• 16 m

• 11 m

B.

18 m

In 
  
    
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