1. Not drawn accurately Rectangles $A B C D$ and $E F G H$ are similar. \[ \begin{array}{l} A B=3 \mathrm{~cm} \\ B C=7 \mathrm{~cm} \\ E F=9 \mathrm{~cm} \end{array} \] Work out the length of FG.

Step 1 ：Given that rectangles ABCD and EFGH are similar, we can set up a proportion to find the length of FG: \(\frac{AB}{EF} = \frac{BC}{FG}\)

Step 2 ：Substitute the given values: \(\frac{3}{9} = \frac{7}{FG}\)

Step 3 ：Solve for FG: \(FG = \frac{7 \times 9}{3}\)

Step 4 ：Calculate the value: \(FG = 21\)

Step 5 ：\(\boxed{FG = 21 \text{ cm}}\)