UPSC CAPF Assistant Commandant Model Paper 7

GIVEN:
Distance between two cars = 64 km apart
Speed of one car = 48 km/h
t1−t2=30
CONCEPT:
Speed, time and distance
FORMULA USED:
Distance = Speed × Time
CALCULATION:
Let speed of second car = ‘x’
Relative speed of cars = (48 + x)
Now,
64 − 4 = (48 + x) ×

t1

60

⇒ (48 + x) t1 = 3600 ...1)
84 − 64 = (48 + x) ×

t2

60

⇒ (48 + x) t2= 1200 ...2)
From (1) and (2):
t1 / t2 = 3/ 1
Let t1 = 3a and t2= a
t1−t2=30
⇒ 3a – a = 30
⇒ a = 15
(48 + x) × 3 × 15 = 3600
⇒ 48 + x = 80
⇒ x = 32
∴ Speed of second car = x = 32 km/h