The period T of a pendulum is given by:

where L is the length of the pendulum while

is the gravitational acceleration.
In the pendulum of the problem, one complete vibration takes exactly 0.200 s, this means its period is

. Using this data, we can solve the previous formula to find L:
<span>d. 93 billion miles
</span>Earth, being the third planet from the sun is unique in the universe because it is currently the only planet known to support life. Earth's distance from the sun is really one of the key reasons why it is has widespread life.Earth occupies what scientists sometimes call the Goldilocks zone. Its distance from the sun means its neither too hot nor too cold to support liquid water. Water is thought to be a key ingredient for life.<span> The energy from the sun in just the right intensity and the availability of water on the earth make it possible for life to thrive on earth. Plants use both these resources for photosynthesis and make nutrients that are available to support the life of animals on the earth. </span>

λ - wavelength, c - the speed of light, f - frequency
![f=200 \ kHz= 200 000 \ Hz \\ \\ \lambda=\frac{300 000 \ [\frac{km}{s}]}{200 000 \ [Hz]}=\frac{3}{2}=1.5 \ [km]](https://tex.z-dn.net/?f=f%3D200%20%5C%20kHz%3D%20200%20000%20%5C%20Hz%20%5C%5C%20%5C%5C%0A%5Clambda%3D%5Cfrac%7B300%20000%20%5C%20%5B%5Cfrac%7Bkm%7D%7Bs%7D%5D%7D%7B200%20000%20%5C%20%5BHz%5D%7D%3D%5Cfrac%7B3%7D%7B2%7D%3D1.5%20%5C%20%5Bkm%5D)
The wavelength of these waves is 1.5 km.