A) 28 km/h
B) 30 km/h
C) 40 km/h
D) 20 km/h
Correct Answer: D
Solution :
Let the normal speed be \[x\,\,km/h,\] then \[\frac{80}{x}-\frac{80}{(x+4)}=1\] \[\Rightarrow \] \[{{x}^{2}}+4x-320=0\] \[\Rightarrow \] \[x(x+20)-16(x+20)=0\] \[\Rightarrow \] \[(x+20)\,(x-16)=0\] \[\Rightarrow \] s\[x=16\,\,km/h\] \[\therefore \] \[(x+4)\,=20\,\,km/h\] Therefore, increased speed = 20 km/hYou need to login to perform this action.
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