72% of what number is 648

To solve this you set up an equation. You have an unknown number, call it "X", and you know that 72% of X is equal to 648. Taking 72% of something is like multiplying it by 0.72, so you have:


0.72 \times X = 648


Now you can divide both sides by 0.72:

\frac {0.72 \times X } {0.72} = \frac {648} {0.72} \\
\frac {\cancel{0.72} \times X } {\cancel{0.72}} = \frac {648} {0.72} \\
X = \frac {648} {0.72}


Can you take it from here?