Question

The value of y varies directly with x. If y is 31.5 when x is 9, what is the value of x when y is 49?

Answer 1

You have that y varies directly with x, it means tha you can write the relation between both variables as follow:

`y=kx`

where k is the constant of proportionality.

If y = 3.15 when x = 9, you can find the value of k, just as follow:

`k=(y)/(x)=(3.15)/(9)=0.35`

Then, the equation that relates y and x can be writen as follow:

`y=0.35x`

or

`x=(y)/(0.35)`

Now, you can find the value of x when y = 49, by replacing this value into the previous equation:

`x=(49)/(0.35)=140`

Hence, the value of x when y = 49 is x = 140