Question

15 is 30% of what number?

Answer 1

`15\ is\ 30\%\ of\ x\\\\30\%=(30)/(100)=(3)/(10)=0.3\\\\15\ is\ 0.3\ of\ x\\\\therefore\\\\0.3x=15\Rightarrow x=15:0.3\\\\\boxed{x=50}\\\\other\ method:`



`\begin{array}{cccc}30\%&-&15&|divide\ both\ sides\ by\ 3\\\\10\%&-&5&|multiply\ both\ sides\ by\ 10\\\\100\%&-&50&-solution\end{array}`