Two puppies which are 520 feet apart are running towards each other. their speeds are 4 and 5 feet per second. how much time will elapse before they are 250 feet apart from each other?

30 seconds

Step-by-step explanation:

Find the total distance needed to be traveled. 520-250 = 270

Find combined rate. 4+5=9

Divide distance needed to be traveled by combine rate to get answer.

270/9 = 30.

30 seconds

Step-by-step explanation:

The first puppy is running at a rate of 4 feet per second; letting t represent the number of seconds, this is 4t.

The second puppy is running at a rate of 5 feet per second; this is 5t.

In order for them to be 250 feet apart, they would have run 520-250 = 270 feet.

Together their combined distances will be 4t+5t, and it will equal 270:

4t+5t = 270

9t = 270

Divide both sides by 9:

9t/9 = 270/9

t = 30

It would take 30 seconds.

The first puppy would travel 4(30) = 120 feet, and the second puppy would travel 5(30) = 150 feet; this is a total of 120+150 = 270 feet.  This leaves them 520-270 = 250 feet apart.