Question

A journey takes 4 hours 30 minutes at a speed of 60 km/h. How long will the same journey take at a speed 15m/sec

Answer 1

given ,
speed = 60kmph = 50/3m/s
time = 4hr 30 min = 4×60+30min= 240+30=270min
time = 270×60 = 16200seconds
distance = speed × time
distance = 16200×50/3
distance = 5400×50m
distance = 270000m
distance = 270 km
given , new speed = 15 m/s
distance = 270000m
time = distance / speed
time = 270000/15
time = 90000/5
time = 18000s
new time = 18000s = 300 min = 5 hours

Answer 2

Step-by-step explanation:

60 kmph =

60 × 5

m/sec

18

=

50

m/sec.

3

∴ Speed ∝

1

Time

⇒ S1 × T1 = S2 × T2

⇒

50

×

9

= 15 × T2

3 2

⇒ T2 =

75

= 5 hours

15

Second Method :

Here, S1 = 60, t1 = 4

1

=

9

2 2

S2 = 15 ×

18

= 54

5

S1t1 = S2t2

60 ×

9

= 54 × t2

2

t2 =

270

= 5 hours

54