Question 322587
let the original speed be x
5/7 of the speed = 5x/7
..
48 seconds = 48/3600 hours = 1/75 hours
40 ninutes = 40/60 =2/3 hours
1 hour
so total time in hours = 1+2/3 +1/75
75+50+1 / 75=126/75 hours

speed = distance / time
speed = 42 / 126/75
speed= 42*75/126
5x/7= 25
5x=25*7
x= 25*7/5
x=35
x= 35 km/h