Question : What is the minimum distance (in metres) required to hear an echo?

Option 1: 10

Option 2: 13

Option 3: 17

Option 4: 21

Question : The upper part of a tree broken at a certain height makes an angle of 60° with the ground at a distance of 10 metres from its foot. The original height of the tree was:

Option 1: $20\sqrt{3}$ metres

Option 2: $10{\sqrt3}$ metres

Option 3: $10\left (2+{\sqrt3} \right)$ metres

Option 4: $10\left (2-{\sqrt3}\right)$ metres

Question : Sound travels 330 metres in a second. When the sound follows the flash of lightning after 10 seconds, the thundercloud will be at a distance of:

Option 1: 1300 metres

Option 2: 2000 metres

Option 3: 3650 metres

Option 4: 3300 metres

Question : The shadow of a tower when the angle of elevation of the sun is 45°, is found to be 10 metres longer than when it was 60°. The height of the tower is:

Option 1: $5\sqrt{3}-1$ metres

Option 2: $5(3+\sqrt{3})$ metres

Option 3: $10(\sqrt{3}-1)$ metres

Option 4: $10(\sqrt{3}+1)$ metres

Question : A boat running upstream takes 10 hours to cover a certain distance, while it takes 7 hours to cover the same distance running downstream. What is the ratio between the speed of the boat and that of the water current, respectively?

Option 1: 17 : 5

Option 2: 3 : 17

Option 3: 2 : 17

Option 4: 17 : 3

Question : The top of a broken tree touches the ground at a distance of 15 metres from its base. If the tree is broken at a height of 8 metres from the ground, then the actual height of the tree is:

Option 1: 17 metres

Option 2: 20 metres

Option 3: 25 metres

Option 4: 30 metres