after t hours after 9AM, the distance will be
√((3*(t+3))^2+(3.5t)^2)
so you need to solve
√((3*(t+3))^2+(3.5t)^2) = 30
21.25t^2 + 54t + 81 = 900
t = 5.0663
Let's just call it t=5, so that would be 2PM
or, you can include the minutes if you want...
Steve and Elsie are camping in the desert, but have decided to part ways. Steve heads north, at 6 AM, and walks steadily at 3 miles per hour. Elsie sleeps in, and starts walking west at 3.5 miles per hour starting at 9 AM.
When will the distance between them be 30 miles? (Round your answer to the nearest minute.) pm
3 answers
let T be the amount of time (in hours) after Elsie starts walking
[3 * (3 + T)]^2 + (3.5 T)^2 = 30^2
(3 T + 9)^2 + (3.5 T)^2 = 900
9 T^2 + 54 T + 81 + 12.25 T^2 = 900
21.25 T^2 + 54 T - 819 = 0 ... solve the quadratic for T
[3 * (3 + T)]^2 + (3.5 T)^2 = 30^2
(3 T + 9)^2 + (3.5 T)^2 = 900
9 T^2 + 54 T + 81 + 12.25 T^2 = 900
21.25 T^2 + 54 T - 819 = 0 ... solve the quadratic for T
you can include minutes
1 answer