Question:
A girl is sitting in the middle of a park of dimension $12 \mathrm{~m} \times 12 \mathrm{~m}$. On the left side of it, there is a building adjoining the park and on the right side of the park, there is a road adjoining by park. A sound is produced on the road by a cracker. Is it possible for the girl to hear the echo of this sound? Explain your answer.
Solution:
To hear echo, the distance between the source of sound and the obstacle (i.e., building) should be more than $17 \mathrm{~m}$. In this case, distance between source of sound (i.e., cracker) and the obstacle (i.e., building) is $12 \mathrm{~m}$ i.e., less than $17 \mathrm{~m}$. Hence, girl cannot hear the echo of the sound of the cracker.