Question
CIVICS > ELECTION_COMMISSION
1) A train 800 metres long is running at a speed of 78 km/hr. If it crosses a tunnel 1 minute, then the length of the tunnel (in meters) is
A) 130 mB) 360 m
C) 500 mD) 540 m
View Answer        RRB_SE_Green_Answer_key_2014
Answer : 500 m

egin{aligned} ext{S1 = 78 }frac{km}{hr}\ ext{L = 800 m}\ ext{T = 1 min}\ ext{Converting }frac{km}{hr} ext{ to }frac{m}{sec} ext{ using }frac{5}{18}\ ext{S1 = }left(frac{78 * 5 }{ 8} ight) frac{m}{sec} = left(frac{65}{3} ight)frac{m}{sec}\ ext{Converting Time from min to sec}\ ext{T = 1 min =60 sec}\ ext{Let length of the tunnel be y metres}\ ext{Therfore, }left(frac{800 + y}{60} ight)=frac{65}{3}\ ext{3 ( 800 + y ) = 3900}\ ext{x = 500}\ end{aligned}



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