# related rates

#### mr.burger

##### New member
Two Trucks leave the same intersection one traveling East at 45 mph and the other traveling North at 60 mph. At what rate is the distance between them changing at 2 pm if they both leave at noon? If the north bound leaves at noon and east bound at 1 pm.?

#### Gene

##### Senior Member
The eastbound truck is at P(45t,0)
The northbound truck is at P(0,60t)
They form a right triangle so the distance between them is
D = sqrt((45t)^2+60t)^2)
find dD/dt at t=2

The eastbound truck is at P(45(t-1),0)
The northbound truck is at P(0,60t)
Same problem

I assume you needed help with the equations, not the derivitives.

#### mr.burger

##### New member
is the answer to the first one 150 mph and the second one 128.2 mph????

#### Gene

##### Senior Member
Nope, try again. You might show your work too. It can't possibly be more than 60+45. That would be if they were heading directly away from each other.

#### mr.burger

##### New member
is the answer 1.4 mph and 12 mph??????????

#### Gene

##### Senior Member
Nope. It is at least 60-45. That is the smallest it could be (if they were going the same direction.) Now you know 15<x<105.
You might show your work.