Question

Y is directly proportional to the square root of x if y = 60 when x = 36 find x when y = 80

Answer 1

Answer:

x = 64

Step-by-step explanation:

Given y is directly proportional to $\sqrt{x}$ then the equation relating them is

y = k$\sqrt{x}$ ← k is the constant of proportion

To find k use the condition y = 60 when x = 36, then

60 = k $\sqrt{36}$ = 6k ( divide both sides by 6 )

10 = k

y = 10$\sqrt{x}$ ← equation of proportion

When y = 80 , then

80 = 10$\sqrt{x}$ ( divide both sides by 10 )

8 = $\sqrt{x}$ ( square both sides )

64 = x

Answer 2

Y = x^2
80 = x^2
x = √80
x = 8.94