Question

A man completed a trip of 136km in 8 hours some part was covered in 15 km/ hr and remainng at 18 km/ hr find the part of trip covered at18km / hr

Answer 1

total time taken =8hrs
X+Y=8. .........eq-1
some part is covered in 15 and 18 speeds
15X+18Y=136. ..........Eq-2
multiplying eq 1 by 15
15X+15Y=120
15X+18Y=136. (-)
-3Y=-16
Y=5.33
so X=2.67
so part of trip travelled in 18kmph=18x2.67
=48km

Answer 2

Let x be the distance traveled at the speed of 15 km/hr and y be the distance traveled at the speed of 18km/hr.


Given x + y = 136 ---- (1) 

          x/15 + y/18 = 8   

         18x + 15y = 2160   --- (2)

On solving (2) and (1)*18 we get

y = 96 

Substitute y = 96 in (1), we get

x = 40.

Hence 18km/hr of trip covered by 96km/hr and 15km/hr covered by 40km.