Question

a car has to cover a distance of 100km in 1hr50min.if it travels first 36km for at 72km/hr at what speed must it travel for restof the distance in order to complete the journey in time.?

Answer 1

total distance = 100
time taken = 1 hr 50 min = 60+50=110 min
It travels first 36 km at the speed of 72 km/hr,
Thus time taken in travelling 36 km would be 36/72 hrs = 30 min
distance left = 100-36 = 64
and time left = 110-30 = 80 min = 4/3 hrs
Thus speed would be distance / time = 64*3/4 = 48 km/hr

Answer 2

GIVEN :
time = 1hr 50 min = 1 50/60 hr = 11/6 hr
Distance = 100 km
Speed = s/t
= (100/11) ×6
= 600/11 km/hr


S = 36 km
v = 72 km/hr
t = s/v
= 36/72
= 1/2 hr

remaining time = 11/6 -1/2
= 11-3/6
= 8/6
= 4/3 hr

remaining distance = 100-36
= 64

speed = s/t
= (64/4) × 3
= 16×3
= 48 km/hr


therefore the speed must be 48km/hr

hope this helped you ......