Aaron and Bob start walking from the same point in a straight line. Aaron walks at 5km/h while Bob walks at 7km/h. Their dog runs continuously between them at an average speed of 15 km/h (in other words when the dog sees Bob it instantly turns around to go back to Aaron and back). How many km has the dog run after 2 hours?



Answer :

Answer:

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Step-by-step explanation:

To find out how far the dog has run after 2 hours, we can consider the relative speeds of Aaron, Bob, and the dog.

Let's denote:

Aaron's speed as

5

km/h

5km/h

Bob's speed as

7

km/h

7km/h

The dog's speed as

15

km/h

15km/h

Since the dog runs back and forth between Aaron and Bob, it effectively runs at the sum of their speeds. Therefore, the relative speed of the dog with respect to Aaron is

15

km/h

+

5

km/h

=

20

km/h

15km/h+5km/h=20km/h, and with respect to Bob, it is

15

km/h

+

7

km/h

=

22

km/h

15km/h+7km/h=22km/h.

Now, let's calculate the distance each of them covers in 2 hours:

Aaron:

5

km/h

×

2

h

=

10

km

5km/h×2h=10km

Bob:

7

km/h

×

2

h

=

14

km

7km/h×2h=14km

The dog will run for the same duration as Aaron and Bob, so we'll consider the distance covered by the dog when moving towards Aaron and when moving towards Bob.

The distance covered by the dog moving towards Aaron in 2 hours is:

Distance

=

Speed

×

Time

=

20

km/h

×

2

h

=

40

km

Distance=Speed×Time=20km/h×2h=40km

The distance covered by the dog moving towards Bob in 2 hours is:

Distance

=

Speed

×

Time

=

22

km/h

×

2

h

=

44

km

Distance=Speed×Time=22km/h×2h=44km

Now, we add up the distances covered by the dog when moving towards Aaron and when moving towards Bob:

Total distance covered by the dog

=

40

km

+

44

km

=

84

km

Total distance covered by the dog=40km+44km=84km

So, the dog has run a total of

84

84 kilometers after 2 hours.