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advincula
Y is directly proportional to X where Y=81 and X=9 Find Y if X=7 ..... i will wait for the answer . thanks :))
y=kx Putting Y=81 and X=9, we get, k=9 Now when x=7 y=7x9=63
k=constant of proportionality
\[y(x)\propto x\]\[y(x)=kx\] \[y(9)=k\times9=81\]\[\qquad\qquad k=\frac{81}9\] \[y(7)=k\times7=\frac{81}9\times7\color{grey}=\]