Question

Solve & earn 20 pts. Class 10

Answer 1

we have required length of the journey.
first we have to find out speed of ship and original time taken to cover the length of journey. let the speed of ship is S km/h 
    time taken by ship is T h.
hence, distance ( length of journey ) = speed of  ship * time 
                                        = ST km  ---------(1)
  a/c to question,
        if speed of ship = ( S + 6 ) km/h
            then , time taken to covers length of journey = (T - 4) h
        e.g.,  length of journey = ( S+ 6 )(T - 4) 
               ST =   ST - 4S +6T - 24  { from eqn (1) length of journey = ST
    6T - 4S = 24 ----------------(2)

again, 
    if speed of ship = (S - 6 ) km/h
      time taken to cover lenght of journey = (T + 6 )h
e.g., length of journey = (S - 6)(T + 6) 
                ST = ST + 6S - 6T -36 
     -6T + 6S = 36 -----------------------------(3) 

now solve equations (2) and (3) 
   2S = 24 + 36 = 60 ⇒ S = 30 km/h 
now put it in equation (2) 
    T = 24 hr 

hence, length of journey = ST = 30 * 24 = 720 km
   

Answer 2

the length of the journey was 720 km.
Hope this will help u.