A) 80
B) 70
C) 72
D) 90
Correct Answer: A
Solution :
[a] Let the distance between P and Q is x and large number is 4x. Then, according to the question, \[\frac{x\times \frac{1}{4}}{10}+\frac{x\times \frac{3}{4}}{12}=7\] \[\Rightarrow \] \[\frac{x}{40}+\frac{3x}{48}=7\] \[\Rightarrow \] \[\frac{x}{40}+\frac{x}{16}=7\] \[\Rightarrow \] \[\frac{2x+5x}{80}=7\] \[\Rightarrow \] \[7x=80\times 7\] \[\therefore \] \[x=80\,km\] |
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