Question

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?​

Answer 1

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

`y\propto x`

`y=kx` ...(i)

where, k is constant of proportionality.

Putting y=45 and x=180, we get

`(45)=k(180)`

`(45)/(180)=k`

`k=(1)/(4)`

Substituting
`k=(1)/(4)` in (i), we get

`y=(1)/(4)x`

Put x=80 in this equation.

`y=(1)/(4)(80)`

`y=20`

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