Question

At noon boat A is 100 km West of boat B. A is moving at 25 km/h South, and B is moving at 35 km/h North. At what rate is the distance between A and B changing at 4pm?

Answer 1

The change on horizontal distance (y) is 0

Answer 2

@Ahmad-nedal thanks so much! How did you get 500?

Answer 3

Oops I'm sorry. It's 240
Since (35+25)*4=240
The speeds add up since they go in opposite directions

Answer 4

The two boats can never be moving at a rate more than 70km/h away from one another.

Answer 5

I'm afraid there are other mistakes, if the idea is clear, just forget about the final numbers

Answer 6

Right, I don't quite understand [t(35+25)] this part.. i mean the logic behind it

Answer 7

Ahh okay, so using Pythag we always know the distance between the two boats...

Answer 8

't' being the time passed in hours.
Distance^2 = 100^2 + [(35+25)t]^2

Answer 9

U want the distance in the equation, which is x in this case,
Distance=time*speed=x
From that you can also find z, the other distance

Answer 10

Ex: after an hour, the boats will be 100km apart on the x-axis, and 70km apart on the y-axis right?

after 2hrs, the boats will still be 100km apart on the x-axis, but 140km apart on the y-axis