after the train passed, the pitch of the train whistle became lower. this change in sound would be represented by what change in the diagram above?

a. the distance represented by ''a'' would increase.
b. the distance represented by "a" would decrease.
c.the distance represented by ''c" would increase.
d. the distance represented by "c" would decrease.

A. The distance represented by ''A'' would increase.

Explanation:

The pitch of a sound is how we perceived the frequency of a sound: the higher the frequency, the higher the pitch, the lower the frequency, the lower the pitch.

In this problem, we have a train passing us, and after that, the pitch of the train whistle became lower: this means that the frequency also becomes lower. This effect is known as Doppler effect.

So, we said that the frequency of the sound wave decreases: this means that the wavelength (which is inversely proportional to the frequency) increases. From the graph, we see that the wavelength (distance between two adjacent crests) is represented by 'A': therefore, since we concluded that A must increase, the correct answer is

A. The distance represented by ''A'' would increase.

$500 X 0.20 = $100

500-100=$400 Remaining

400 X 0.25 = $100

400-100=$300

he have spend $200