+0  
 
0
54
5
avatar+134 

Sel run around a track 3 times in 8 minutes. Mar  run around the same track 2 times in 5 minutes.If sel and Mar begin at the same time and same place, what is the combined number of laps they both would have run when they next reach starting point at same time? 

dgfgrafgdfge111  Nov 21, 2018
edited by dgfgrafgdfge111  Nov 21, 2018
 #1
avatar+92787 
0

You left out the number of times that Sel ran around the track.....

 

 

cool cool cool

CPhill  Nov 21, 2018
 #2
avatar+134 
+2

Sorry, its 3.

dgfgrafgdfge111  Nov 21, 2018
 #3
avatar+92787 
+2

Sel runs  3/8 lap in one minute

Mar runs 2/5 lap in one minute

 

So.... Mar runs  (2/5 - 3/8) =  [ 16 - 15] / 40    =  1/40   of a lap farther than Sel does in one minute

 

So....in 40 minutes....they will be even again

 

In this time     Sel runs (3/8)*40 = 15 laps

And Mar runs (2/5)*40 =  16 laps

 

So...combined.....they run 15 + 16   = 31 laps

 

 

cool cool cool

CPhill  Nov 21, 2018
 #4
avatar+134 
+3

Thank you.

dgfgrafgdfge111  Nov 22, 2018
 #5
avatar+14578 
+2

3L/8min    2L/5min     find(lowest) common denominator  (40)

 

15L/40min      16L/40min         At 40 minutes they will have combined 15+16 = 31 laps

 

(added 'lowest')

ElectricPavlov  Nov 22, 2018
edited by ElectricPavlov  Nov 22, 2018

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