SOLUTION: if a man and a boy can do a work in 8 days,this work can do 2 man and 4 boy in 3 days .how many days it will takes if a man or a boy do alone?

Question 718048: if a man and a boy can do a work in 8 days,this work can do 2 man and 4 boy in 3 days .how many days it will takes if a man or a boy do alone?
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = the rate that the man works
Let = the rate that the boy works
Add their rates to get rate working together
( 1 job ) / ( 8 days ) is rate working together, so
(1)
-----------------------------
Then you are given the case with 2 times the rate for a man
and 4 times the rate for a boy
(2)
-------------------------------
Multiply both sides of (1) by
and subtract (1) from (2)
(2)
(1)

and, since
(1)
(1)
(1)
(1)
(1)
------------------------
A man, working alone can do 1 job in 12 days
A boy, working alone, can do 1 job in 24 days
-----------------
check the answer:
(2)
(2)
(2)
(2)
OK

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