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
[tex]y\propto x[/tex]
[tex]y=kx[/tex] ...(i)
where, k is constant of proportionality.
Putting y=45 and x=180, we get
[tex](45)=k(180)[/tex]
[tex]\dfrac{45}{180}=k[/tex]
[tex]k=\dfrac{1}{4}[/tex]
Substituting [tex]k=\dfrac{1}{4}[/tex] in (i), we get
[tex]y=\dfrac{1}{4}x[/tex]
Put x=80 in this equation.
[tex]y=\dfrac{1}{4}(80)[/tex]
[tex]y=20[/tex]
Therefore, the value of y is 20 when x=80.
