Andrea was watching her brother in the ocean and noticed that the waves were coming into the beach at a frequency of 0.571429 Hz. How many waves hit the beach in 28 s? Answer in units of waves.

16 waves

Explanation:

This is actually pretty easy to understand.

First we have the frequency "f" of the waves which is 0.571429 Hz and we want to know how many waves will hit the beach in 28 s. To know this, we need to know the period time of the waves, this can be calculated with the frequency and the following expression:

T = 1/f

With this expression we can calculate the period time of the waves. So replacing the data:

T = 1 / 0.571429

T = 1.749999 s

Now that we have the period, this number means that every 1.75 s, a wave hit the beach. Now to know the number of waves in 28 s, we just divide the period with the given time:

n = t/T

Replacing we have:

n = 28 / 1.749999

1.solid

2.carbon dioxide

3.helium