Question
CIVICS > ELECTION_COMMISSION
1) A car travels 70 km in one hour before some fault happens, then it travels for 120 km at 30 kmph. For the entire trip, what was the average speed
A) 33 kmphB) 36 kmph
C) 38 kmphD) 40 kmph
View Answer        RRB_JE_2014_Answer-key
Answer : 38 kmph

egin{aligned} ext{D1=70 km}\ ext{T1=1 hr}\ ext{D2=120 km}\ ext{S2=30 km/hr}\ ext{Average speed=}frac{2xy}{left(x+y ight)}\ ext{T2 = }frac{120}{30}=4 hr\ ext{S1=}frac{D1}{T1}=frac{70}{1}= 70 km/hr\ =frac{2*70*30}{left(70+30 ight)}\ =frac{2*2100}{100}=2*21=42 km/hr\ end{aligned}




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