Question

Steve travels 2 times as fast as Jill. Traveling in opposite directions, they are 120 miles apart after 2.5 hours. Find their rates of travel.

Answer 1

let's recall that d = rt, distance = rate * time.

we know that Steve is twice as fast as Jill, so say if Jill has a speed or rate of "r", then Steve is traveling at 2r fast, now we know they both in opposite directions have covered a total of 120 miles, so if Jill covered "d" miles then Steve covered 120 -d, check the picture below.

$\begin{array}{lcccl} &\stackrel{miles}{distance}&\stackrel{mph}{rate}&\stackrel{hours}{time}\\ \cline{2-4}&\\ Jill&d&r&2.5\\ Steve&120-d&2r&2.5 \end{array}~\hfill \begin{cases} d=2.5r\\[2em] 120-d=5r \end{cases} \\\\\\ \stackrel{\textit{substituting on the 2nd equation}}{120-2.5r=5r\implies 120=7.5r}\implies \cfrac{120}{7.5}=r\implies \stackrel{Jill's}{16=r}~\hfill \stackrel{Steve's}{32}$