Question

If y varies directly as x, and y=7 when x=3, find y when x=7

Answer 1

option A is correct, i.e. y = 7x/3 ; y(7) = 49/3.

Explanation:

If y varies directly as x, we can write its relationship as given below:-

y = m*x

where m is the slope of the line on its graph.

Given y=7 when x=3, we can substitute these values in the equation and find m as follows:-

7 = m*3

m = 7/3

So, the required equation is as follow:-

y = 7/3 x

Finding y when x=7, substitute x=7 in the above equation,

y = (7/3)*(7) = 49/3

Hence, option A is correct, i.e. y = 7x/3 ; y(7) = 49/3.

Answer 2

Answer: OPTION A

Explanation:

Direct variation, by definition, has the form shown below:

y=kx

Where k is the constant of proportionality.

Given the information in the problem , you can find k:

`7=3k`

`k=7/3`

Now you can find y when x=7 as following:

`y=(7/3)x`

Substitute values. Then:

`y=(7*7)/3\\y=49/3`