Question

A car travelling at 60 km/hr left Dehradun at 3 P.M. One hour later, another car travelling at 80 km/hr started over the same road to overtake the first. How long must the second car travel to overtake the first car.

Answer 1

$by \:D = v[t]$

On overtaking ,both travel the same distance .

$let \:the \:time \:taken \:by \:2^{nd} \:car \:as \:'t'$

$80t = d$

$60(t+1) =d$

$from \:i \:and \:ii$

$80t=60(t+1)$

$80t=60t+60$

$80t-60t=60$

$20t=60$

$t= \frac{60}{20} = 3$

$so \:t \: = 3$

$t+1=3+1=4$

so distance it taken is..........

$d=t(v) \: 60(4) \: = 240km$

Answer 2

Answer:

3 hrs .

Step-by-step explanation:

Speed of car leaving Dehra Dun at 3 P.M = 60 km/hr .

Car leaving at 80 km/hr travel the same distance .

Distance = speed × time .

Case 1

D = 60  × ( t + 1 )

Case 2

D = 80 t

According to problem :

80 t = 60 ( t + 1 )

⇒ 80 t = 60 t + 60

⇒ 20 t = 60

⇒ t = 60/20

⇒ t = 3

ANSWER IS 3 hours.