A) 7 cm
B) 4 cm
C) 8 cm
D) 9 cm
Correct Answer: A
Solution :
| [a] Given, \[ar\,(\Delta ABC)=25\,c{{m}^{2}},\] |
| \[ar\,(\Delta PQR)=49\,c{{m}^{2}}\] |
| and \[QR=9.8cm\] |
| \[\Delta ABC\tilde{\ }\Delta PQR\] |
| \[\therefore \,\,\,\,\,\,\,\,\,\frac{ar(\Delta ABC)}{ar(\Delta PQR)}=\frac{B{{C}^{2}}}{Q{{R}^{2}}}\] |
| \[\Rightarrow \,\,\,\,\,\frac{25}{49}=\frac{B{{C}^{2}}}{{{(9.8)}^{2}}}\Rightarrow \sqrt{\frac{25}{49}}=\frac{BC}{9.8}\] |
| \[\Rightarrow \,\,\,\,\,\frac{5}{9}\times 9.8=BC\,\,\,\,\,\,\,\,\Rightarrow \,\,\,\,\,\,BC=7cm\] |
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