For this case we have to:
Let [tex]l_ {1} = 11 \ cm[/tex] and [tex]w_ {1} = 10[/tex] \ cm, respectively, the length and width of the first rectangle.
Let [tex]l_ {2}[/tex] and [tex]w_ {2} = 7 \ cm[/tex], respectively, the length and width of the second rectangle.
If both rectangles are similar, it is true that:
[tex]\frac {l_ {2}} {l_ {1}} = \frac {w_ {2}} {w_ {1}}[/tex]
Substituting:
[tex]\frac {l_ {2}} {11} = \frac {7} {10}\\\frac {l_ {2}} {11} = 0.7\\l_ {2} = 11 * 0.7\\l_ {2} = 7.7 \ cm[/tex]
Answer:
[tex]7.7 \ cm[/tex]
