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Kelly took 4 hours to paint a room. Richard took 8 hours to paint an identical room. If both of them worked together, how long would they take to paint the room?

 Apr 22, 2021
 #1
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+1

Here's  an  easy  way  to  do this

 

1/4  +   1/8    =

 

2/8  + 1/8  =

 

3/8

 

Take the   reciprocal of this fraction  =   8/3   =   hrs  to paint the  room if they  work together  =  2 + 2/3 hrs = 

 

2hrs  40 min

 

 

cool cool cool

 Apr 22, 2021
 #2
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+1

Kelly painting rate =   1 room / 4hours = 1/4

Richard painting rate = 1 room / 8hours = 1/8

Remember    job / rate = time       ( or distance / rate = time)

 

Now combine the rates

 

1 room / ( 1/4 + 1/8)  =   1 / (2/8 + 1/8) = 1/(3/8) =  8/3 hour       2   2/3 hour  for both of them working

 Apr 22, 2021

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