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Superman and flash are running around the world in opposite directions. Superman can go around the world in 2.5 hours, and Flash can do the same in 1.5 hours. Assuming they start at the same time and place, how many times will they pass each other going in opposite directions in a 24 hour period? 

 Apr 20, 2021
 #1
avatar+66 
+1

(1/2.5h)x+(1/1.5h)x=1
x=0.9375

24/0.9375= 25.6

They will pass each other 25 times

 Apr 20, 2021
 #2
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Ok thx!

Guest Apr 20, 2021
 #3
avatar+118505 
+2

THX, BF !!!!

 

Here's another  way to see this

 

Let  the circumference of the Earth  =  C

 

So  every  hour    Superman  covers   C / 2.5   = C /( 5/2) =    (2/5)C

 

And  every hour Fals covers   C /(1/5)   = C / (3/2)  = (2/3)C

 

So...every  hour  they cover   (2/5 + 2/3)  C =   (16/15)C

 

Which  means  that  it  takes them  (15/16)  hrs  to  meet   every time

 

So...the  number of times  they  meet in 24 hrs  =  24 / (15/16) ≈ 25.6  times  ≈  25 times  

 

cool cool cool    

 Apr 20, 2021

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