A) 70 km/hour
B) 40 km/hour
C) 60 km/hour
D) 80 km/hour
Correct Answer: C
Solution :
[c] Let the speed of car be x and other be y Distance covered from A in 5 hrs = 5x Distance covered from B in 5 hrs = 5y ATQ When they travel in same direction Then \[5x-\,5y=100\] \[x-\,y=20\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,...(i)\] ? (i) When they travel towards each other Then ATQ \[\begin{align} & ={{r}_{2}}-\,{{r}_{1}} \\ & {{C}_{2}}-\,{{C}_{1}}=66 \\ & \therefore 2\pi {{r}_{2}}=2\pi {{r}_{1}}=66 \\ & \Rightarrow 2\pi ({{r}_{2}}-\,{{r}_{1}})=66 \\ & \Rightarrow {{r}_{2}}-\,{{r}_{1}}=\frac{66}{2\pi }=\frac{66\times 7}{2\times 22}=10.5\,\,metre \\ \end{align}\] Now, adding eqn (i), & (ii) \[2x=120\] \[x=60\,\,km/hr\] 2x=120 x=60 km/hr
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