Question

If y varies directly as x and y = 10 when x = 2, what is y when x = 3?

Answer 1

`y = 15`

Explanation:

Given

`y ∝ x`

`y = kx`

When `y = 10`, `x = 2`

`10 = k × 2`

`k = 10/2`

`k = 5`

When `x = 3`

`y = k × 3`

`y = 5 × 3 = 15`

Answer 2

`y=15`

Explanation:

`"the initial statement is "ypropx`

`"to convert to an equation multiply by k the constant"`
`"of variation"`

`rArry=kx`

`"to find k use the given condition"`

`y=10" when "x=2`

`y=kxrArrk=y/x=10/2=5`

`"equation is " color(red)(bar(ul(|color(white)(2/2)color(black)(y=5x)color(white)(2/2)|)))`

`"when "x=3" then"`

`y=5xx3=15`