Question

A man completed a trip of 136 km in 8 hours.some part of the trip was covered at 15 km/hr and the remaining at 18 km/hr.find the part of the trip covered in 18 km/hr.

Answer 1

Total distance of the trip = 136 km.

Let part of the trip covered at 18 km/hr. = x km.

∴ Distance of the trip covered at 15 km/hr = (136-x) km

Time taken by the man to cover x km = DistanceSpeed=x18 hours

Time taken by the man to cover (136-x) km

=136−x15 hours

Total time taken by the man to cover a trip of 136 km = 8 hours

∴x18+136−x15=8⇒x18×90+136−x15×90=8×90[Multiplying each term by 90 because L.C.M. of denominators = 90]⇒5x+6(136−x)=720⇒5x+816−6x=720⇒5x−6x=720−816⇒−x=−96⇒x=96

∴Part of the trip covered at 18 km/hr = 96 km