A man rides at the rate of 18 km/hr, but stops for 6 minutes to change horses at the end of every 7th km. The time that he will take to cover a distance of 90 km is :
A man rides at the rate of 18 km/hr, but stops for 6 minutes to change horses at the end of every 7th km. The time that he will take to cover a distance of 90 km is :
[A]6 hours
[B]6 hours 12 minutes
[C]6 hours 18 minutes
[D]6 hours 24 minutes
6 hours 12 minutes
90 km = 12 $latex \times$ 7 km + 6 km.
To cover 7 km total time taken = $latex \frac{7}{18}&s=1$ hours + 6 min. = $latex \frac{88}{3}\ min.&s=1$
So, (12 $latex \times$ 7 km) would be covered in $latex \left ( 12\times \frac{88}{3} \right )&s=1$ minutes and remaining 6 km is $latex \frac{6}{18}&s=1$ hours or 20 miutes.
∴ Total time $latex = \frac{1056}{3}+20 = \frac{1116}{3\times 60} = 6\frac{1}{5} \ hours&s=1$
= 6 hours 12 minutes.
Hence option [B] is correct answer.