If y = 1/4 when x=4​, find y when x=5​, given that y varies directly with x.

Question

y=? (fraction)

Answer 1

y varies directly with x:  y = kx  where k is the constant of proportionality

 

y = kx

1/4 = 4k

k = 1/16

 

y = x/16 is your equation.

 

When x = 5 we have:  y = 5/16

 

 

Answer 2

y = k x

 

1/4 = k (5)

 

1/20 = k

 

 y = (1/20) x

 

When x=5, y = (1/20)* 5 = 5/20 = 1/4