15 Ellen is at a hydroplane boat show. Starting from 1.0 miles away, the boat drives towards her and then passes her. The boat passes at a constant rate of 70 miles per hour. Ellen is given by d=l1.0-70tl. At what time is the boat 0.15 miles from Ellen? Calculate your answer in seconds.

D = d + Vt,

d = 1.0 miles,

V = - 70 miles per hour, ( - because its coming towards you)

And about D

Imagine you're standing at the centre of the street. a car is coming towards you. You can easily see that car will be X miles away from you two times. When Driving towards you And When Driving away from you. So

we have two D. + 0.15 miles and - 0.15 miles.

0.15 = 1 - 70t

-0.15=1-70t

From here

t equals

either

0.85/70 hours which is 0.85/70*3600 second about 43.7 sec.

or

1.15/70 hours or 1.15*3600/70 about 59 sec.