Find the constant of variation k. yvaries directly with x; y=400 when x=1000

y = k x
400 = k * 1000
Solve for k

To find the constant of variation (k) when y varies directly with x, we can use the formula:

y = k * x

We are given that y is 400 when x is 1000. Using these values, we can substitute them into the formula and solve for k.

400 = k * 1000

To solve for k, divide both sides of the equation by 1000:

400/1000 = k

0.4 = k

Therefore, the constant of variation (k) is 0.4.