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Frank started out in his car traveling 45 mph. When Frank was 1/3 miles away, Daniel started out from the same point at 50 mph to catch up with Frank. How long will it take Daniel to catch up with Frank?

 Feb 18, 2021
 #1
avatar+120287 
+1

Conversion  factor  from mph  to ft - per - sec  =

 

mph  *  88 /  60

 

45 mph   =   45 *  88  / 60  =  66ft/s

50 mph  = 50 * 88  / 60   = 220/3  ft/ s

1/3  mile  =  5280 ft / 3  =   1760 ft  = the distance  that Daniel  must close to  catch Frank

 

The  difference  in their rates = Daniel's  effective closing rate   =  ( 220/3  - 66 ) ft/s

 

So....the time  (in seconds) to catch Frank  is

 

Distance  to close /  eff. closing rate

 

(1760)  /( 220/3  - 66)   =  240  sec  =   4 min

 

 

cool cool cool

 Feb 18, 2021
edited by CPhill  Feb 18, 2021
edited by CPhill  Feb 18, 2021
edited by CPhill  Feb 18, 2021
 #2
avatar+32894 
+2

Daniel has to cover 1/3 mile at the difference in speeds (5 m/hr) to catch up

1/3 m / 5 m/hr  = 1/15 hr = 4 minutes

 Feb 18, 2021

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