Final answer:
The speed of a wave is inversely proportional to the square root of the depth of the water. Using this relationship, we can find the value of y when d=25.
Step-by-step explanation:
In this problem, we are given that the speed, v, of a wave is inversely proportional to the square root of the depth, d, of the water. We are also given that when v = 30, d = 400.
To find y when d = 25, we can set up a proportion using the inverse proportionality relationship. Since v is inversely proportional to the square root of d, we can write:
v = k/sqrt(d)
where k is the constant of proportionality.
Plugging in the values we know, we have:
30 = k/sqrt(400)
Solving for k, we find that k = 30 * sqrt(400) = 30 * 20 = 600.
Now we can find y using the proportion:
30 = 600/sqrt(25)
Simplifying, we have:
30 = 600/5
Finally, solving for y, we find that y = 600/5 = 120.