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

Answer:

3 hours

Step-by-step explanation:

Let the second car overtake the first, x hours after it started.

First car travelled for (x + 1) hours.

Distance covered by both the car is same.

Distance covered by first car in (x + 1) hours = 60(x + 1) km

Distance covered by second car in x hours = 80x

∴ 60(x + 1) = 80x

⇒ 60x + 60 = 80x

⇒ 60 = 80x - 60x

⇒ 60 = 20x

⇒ $\bold{\dfrac{60}{20}}$ = x

⇒ 3 = x

Hence, the second car travelled in 4 hours.

Answer 2

distance travelled by a car traveling at 60 km/h in t hour = 60 t

Now another car started after one hour

So time taken by it is (t-1)

Now distance travelled by another car = 80( t-1)

As distance traveled is equal

So

60 t = 80( t-1)

60 t = 80 t -80

20 t = 80

t= 4

So second car should travel (4-1) = 3 hours to overtake first car