With an average speed of 40, km / h , a train reaches its destination on time. If it goes with an av

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With an average speed of $40\, km / h ,$ a train reaches its destination on time. If it goes with an average speed of $35 \,Km / h ,$ it reaches late by $15$ minutes. The total journey is (in $km$)

A

$30$

B

$40$

C

$70$

D

$80$

Solution

$\frac{x}{35}-\frac{x}{40}=\frac{15}{60}$ or, $\frac{5 x}{35 \times 40}=\frac{1}{4}$

$x=\frac{35 \times 40}{5 \times 4}=70$

Total journey $=70 km$.

Standard 13

Quantitative Aptitude

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