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

Question

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 kmph	B) 36 kmph
C) 38 kmph	D) 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{27030}{left(70+30 ight)}\ =frac{22100}{100}=221=42 km/hr\ end{aligned}