​$$\text{The areas of two similar triangles } \triangle XYZ \text{ and } \triangle LMN \text{ are } 49 \text{ cm}^2 \text{ and } 9 \text{ cm}^2, \text{ respectively. If } LM = 9 \text{ cm}, \text{ then the length of } XY \text{ is:}$$​​

Correct option is A

​$$\text{We know that}\\\text{If } \triangle XYZ \text{ is similar to } \triangle LMN, \text{ then:}\\\frac{\text{Area of } \triangle XYZ}{\text{Area of } \triangle LMN} = \frac{(\text{corresponding side})_1^2}{(\text{corresponding side})_2^2}\\\frac{49}{9} = \frac{(XY)^2}{(9)^2}\\(XY)^2 = 49 \times 9\\XY = 21 \text{ cm}$$​​