Calculus
posted by Keya
at 12 noon ship A is 65 km due north of a second ship B. Ship A sails south at a rate of 14km/hr, and ship B sails west at a rate of 16km/hr. How fast are the two ships approaching each other 1.5 hours later at 1:30pm? Thank You!

Reiny
Making a sketch for the 12 noon position, placing B at the origin and A 65 units up on the yaxis
At a time of t hrs after noon,
let the distance covered by A be 14t
let the distance covered by B be 16t
Draw a line between their positions and call it d km
d^2 = (16t)^2 + (6514t)^2
when t = 1.5
d^2 = 620
d = √620
2d dd/dt = 2(16t)(16) + 2(65 14t)(14)
dd/dt = (256t + 65  196t)/√620
when t=1.5
dd/dt = (256(1.5) + 65  196(1.5))/√620
= 6.22 km/h
check my arithmetic
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