4. The value of y is directly proportional to the value of x. If y = 45 when x = 180, what is the value of y when x = 80?

Given:

The value of y is directly proportional to the value of x.

y = 45 when x = 180.

To find:

The value of y when x = 80.

Solution:

Since the value of y is directly proportional to the value of x, therefore

     ...(i)

where, k is constant of proportionality.

Putting y=45 and x=180, we get

Substituting in (i), we get

Put x=80 in this equation.

Therefore, the value of y is 20 when x=80.

rx and sx

step-by-step explanation: