algebra: finding speed

[ckaizer]

Answer this question from "ask Marilyn". At 60 mph, it takes 60 seconds to travel a mile. At 120 mph, it takes 30 seconds. At what speed would it take 45 seconds?Please help.

 

[tkhunny]

Why is this hard?

\(\displaystyle \L\,\frac{1 mile}{45 sec}*\frac{60 sec}{1 min}*\frac{60 min}{1 hr}\)

 

[pboland]

Doesn't r=dt
45 mph?

 

[tkhunny]

Doesn't r=dt
45 mph?

Tsk, tsk...

60 mph ==> 60 sec
x mph ==> 45 sec
120 mph ==> 30 sec

30 < 45 < 60 so 60 < x < 120