Answer:
4 19/20 hours or 4 hours , 57 minutes
Step-by-step explanation:
Given
In 9 hours Maria can fill a certain order let Say X
In 9/9 hours Maria can fill X/9 of the order
in 1 hour Maria can fill X/9 of the order
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In 11 hours Jim can fill a certain order let Say X
In 11/11 hours Maria can fill X/11 of the order
in 1 hour Maria can fill X/11 of the order
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Therefore total order filled by them in one hour will sum of individual work done by them in one hour.
Mathematically,
total order filled by Jim and maria in one hour = work done by Jim in one + work done by Maria in one hour
total order filled by Jim and maria in one hour = 1/11 + 1/9
=> 
=>20/99 of certain order is filled by both of them in one hour.
=>Total order is one. Hence, to get 1 from 20/99 we need to multiply it with its reciprocal (i.e 99/20) as 20/99 *99/20 = 1
now
=>20/99 of certain order is filled by both of them in 1 hour.
=>multiplying both order and hour with 99/20 we have
20/99 *99/20 of certain order is filled by both of them in 1* 99/20 hour
Thus total order is filled by them in 99/20 hours = 4 19/20 hours.
1 hour has 60 minutes
so 19/20 has 60*19/20 minutes = 57 minutes.
Working together, Jim and Maria will take 4 hours , 57 minutes to fill the order.
