Direct and inverse proportion

Direct and inverse proportion

1. Direct proportion

   • The equation: y=k*x
   • Example
     • If Y is directly proportional to X, when X = 12 and = 3. Find the value of X when Y = 8
       • First, find the constant of proportionality, K. First write the equation-X(pretend there is a direct proportion symbol here)Y. Then turn this into the equation - Y=K*X.
         • Now we need to find K, since we know that X=12 and Y=3, we can rewrite the equation as 3=k*12, then rearrange it to k=3/12. So we know that k=0.25.
           • So we have the complete equation now - Y=0.25*X. All we need to do now is put the numbers in. 8=0.25*X. We can rearrange this to be X=8/0.25
             • When Y=8, X=32