Question

A car can finish a certain joumey in 9 hours at the speed of 72 km/h. By how much should its speed be increased so that it may take only 8 hours to cover the same distance​

Answer 1

Given :-

▪ A car can Finish a certain journey in 9 hours at the speed of 72 km/h .

To Find :-

▪ The speed at which the car should travel so that it will take only 8 hours the same distance.

Solution :-

It is clear from the question that the destination is same in both the cases or simply the distance travelled in both the cases. So let us find the distance travelled,

According to the case 1 , we have

• Speed = 72 km/h
• Time taken = 9 hours

So,

⇒ Distance = Speed × Time taken

⇒ Distance = 72 × 9

⇒ Distance = 648 km

Now, In the case second, we have

• Time = 8 hours
• Distance = 648 km

⇒ Distance = Speed × Time

⇒ 648 = Speed × 8

⇒ Speed = 648 / 8

⇒ Speed = 81 km/h

So, The speed of the car must be 81 km/h in order to travel the same destination in 8 hours.

Answer 2

Given : A car can finish a certain journey in 9 hours at the speed of 72 km/h.

To find : By how much should its speed be increased so that it may take only 8 hours to cover the same distance.

Using formula :

★ Speed increased = Speed traveled/Time taken to cover the same distance.

Calculations :

→ 72 (9)

→ 72 × 9

→ 648 km

→ 648/8

→ 81 km/hr

Therefore, 81 km/hr is the speed be increased, so that it may take only 8 hours to cover the same distance.