Question

Y is directly proportional to the square root of x

if y = 60 when x = 36
find x when y = 80

Answer 1

y = x^2
80 = x^2
x = √80
x = 8.94

Answer 2

x = 64

Explanation:

Given y is directly proportional to
`√(x)` then the equation relating them is

y = k
`√(x)` ← k is the constant of proportion

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

60 = k
`√(36)` = 6k ( divide both sides by 6 )

10 = k

y = 10
`√(x)` ← equation of proportion

When y = 80 , then

80 = 10
`√(x)` ( divide both sides by 10 )

8 =
`√(x)` ( square both sides )

64 = x