Question 322587: A car travelling with 5/7 of its usual speed covers 42 km in 1 hr 40 min 48 sec.What is the usual speed of car? Answer by mananth(16946) (Show Source):
You can put this solution on YOUR website! 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
