Question

Y varies directly with x, y=65 when x=5. How do you find y when x=12?

Answer 1

`156`

Explanation:

`y` varies directly with `x`

`y ∝ x`

`y = kx color(white)(...)["where"\ k = "proportionality constant"]`

When `y = 65, x = 5`

`65 = k × 5`

`k = 65/5 = color(blue)(13)`

When `x = 12`

`y = kx = color(blue)(13) × 12 = 156`