Question

Suppose y varies directly with x. When

x is 4, y is 10. Write the equation that
relates x and y

Answer 1

Answer: y = (5/2)x

Explanation:

y varies directly with x implies that y∝x

To turn y∝x to a full equation, introduce a constant k to the right hand side.

Therefore, y = kx

Given that x is 4 and y is 10, substitute x and y in the equation above.

Then, 10 = 4k

4k = 10

k = 10/4

k = 5/2

Since k = 5/2, then the equation y = kx becomes,

y = (5/2)x