To calculate the speed of sound, we need to understand that an echo involves a sound wave traveling to a surface and back. In this case, the sound travels from the boy to the wall and then returns.
The total distance that the sound wave travels is twice the distance from the boy to the wall because it goes to the wall and back. Therefore, the total distance is:
Total Distance = 2 x 408m = 816m
The echo was heard 2.4 seconds after the sound was made. The speed of sound can be calculated using the formula:
Speed of Sound = Total Distance / Time
Plugging in the values, we have:
Speed of Sound = 816m / 2.4s
When you perform the division, you find:
Speed of Sound = 340 m/s
Thus, the speed of the sound is 340 m/s, which is the correct answer.