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# Calculus Help!!?

Two commercial jets at 40,000 ft are flying at 520 mi/hr along straight line courses

that cross at right angles. How fast is the distance between them closing when the

airplane A is 5 mi from the intersection point and airplane B is 12 mi from the

intersection point? How fast is the distance closing at any time t?

### 1 Answer

- BryceLv 72 months agoFavorite Answer
D²= x² + y²

D= √(5² + 12²)= 13 mi

D*dD/dt= x*dx/dt + y*dy/dt

13*dD/dt= 5*-520 + 12*-520

dD/dt= -680 mi/hr