Question

If y varies directly as x and y =5 when x=2, how do you find y when x=6?

Answer 1

The relationship between x and y is `y=5/2x`, therefore `y=15` when `x=6`

Explanation:

The way I read your question is that we can write the relation between x and y on the form `y=ax`.

In this case we know that `5=a*2` or `a=5/2`, so that the relationship between y and x can be written on the form
`y=5/2x`.

In that case we can just plug in x=6 in the equation, in which case we get
`y=5/2*6=15`

An easy way of finding the same result is with a graph:
graph{y=5/2x [-9.67, 30.87, -1.92, 18.34]}

Reading off our graph we can see that the line goes through (2, 5) and (6, 1).