A) 120 minutes
B) 40 minutes
C) 160 minutes
D) 80 minutes
Correct Answer: C
Solution :
Durga's average speed \[=\left( \frac{2xy}{x+y} \right)\,kmph.\,=\left( \frac{2\times 5\times 15}{5+15} \right)\,\,kmph.\] \[=\left( \frac{2\times 5\times 15}{20} \right)\,kmph=\frac{15}{2}\,kmph\] Distance of school = 5 km. Smriti's speed \[=\frac{15}{4}\,kmph\] \[\therefore \] Required time \[=2\left( \frac{5}{\frac{15}{4}} \right)\] hours \[=\left( \frac{2\times 5\times 4}{15} \right)=\frac{8}{3}\] hours \[=\left( \frac{8}{3}\times 60 \right)\] minutes = 160 minutesYou need to login to perform this action.
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