A) 15 cm
B) 20 cm
C) 25 cm
D) 30 cm
Correct Answer: D
Solution :
Given \[{{v}_{1}}=3x\]and \[{{v}_{2}}=2(x+5)\] So here, 1st case \[\frac{1}{-x}+\frac{1}{-3x}=\frac{1}{f}\] ?(i) \[\frac{1}{-(x+5)}+\frac{1}{-2(x+5)}=\frac{1}{f}\] ?(ii) On solving Eqs. (i) and (ii) we get \[f=30\,cm\]You need to login to perform this action.
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