There are 3 kids in a family-Anna, Peter and Maria. Anna can clean the house
for 1 hour, Peter can do the same job for 3 hours and Maria needs 6 hours.
How much time do they need to work to finish the same cleaning if they do it
together?
Choose the correct option.
A) 20min
B) 40min
C) 30min
D) 50min
E) 60min
In 6 hours, Anna will do 6 times the work, Peter will do   2 times the work and Maria will just finish the work. So if they   work together they would do 9 times the work required in 6 hours.   Answer:40 minutes   correct answer 40min
<result>B</result>
There are 3 kids in a family-Anna, Peter and Maria. Anna can clean the house
for 1 hour, Peter can do the same job for 3 hours and Maria needs 6 hours.
How much time do they need to work to finish the same cleaning if they do it
together?