If w varies jointly as x and y,
and w=10 when x=2 and y=1.
Solve for w when x=4 and y=2

Given:

w varies jointly as x and y.

w=10 when x=2 and y=1.

To find:

The value of w when x=4 and y=2.

Solution:

w varies jointly as x and y.

             ...(i)

Where, k is the constant of proportionality.

w=10 when x=2 and y=1.

The value of k is 5.

Putting k=5 in (i), we get

To find the value of w when x=4 and y=2. Put x=4 and y=2.

Therefore, the value of w is 40 when x=4 and y=2.