A) 205 m
B) 300 m
C) 180 m
D) 270 m
Correct Answer: D
Solution :
For not hearing the echo the time interval between the beats of drum must be equal to time of echo. Þ \[{{t}_{1}}=\frac{2d}{v}=\frac{60}{40}=\frac{3}{2}\] ...... (i) and \[{{t}_{2}}=\frac{2(d-90)}{v}=\frac{60}{60}=1\] Þ \[2d-180=v\] ...... (ii) Form (i), we get\[2d=\frac{3}{2}v\]. Substituting in (ii), we get Þ \[\frac{3}{2}v-180=v\] Þ \[180=\frac{v}{2}\] Þ \[v=360m{{s}^{-1}}\] Þ \[\frac{2(d)}{360}=\frac{3}{2}\] Þ \[d=270m\].You need to login to perform this action.
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