The equation in which b varies directly as the square root of c is b = 50 · √c. (Correct choice: B)
In this problem we have a case of direct variation between two variables, which is mathematically described by a direct proportionality model, whose form and characteristics are shown below:
b ∝ √c
b = k · √c (1)
Where k is the proportionality constant.
First, we determine the value of the constant of proportionality by substituting on b and c and clearing the variable: (b = 100, c = 4)
k = b / √c
k = 100 / √4
k = 100 / 2
k = 50
Then, the equation in which b varies directly as the square root of c is b = 50 · √c. (Correct choice: B)
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