Question

John can paint a fence in 9 hours. tim can paint the same fence in 11 hours. how much time would the two working together need to paint the same fence? (round your answer to the nearest hundredth.)

Answer 1

we know that

John can paint a fence in 9 hours
so
100%----------> 9 hours
X--------------> 1 hour
x=100/9-----> 11.11%
that means that in 1 hour john paint 11.11% of the fence

Tim can paint a fence in 11 hours
so
100%----------> 11 hours
X--------------> 1 hour
x=100/11-----> 9.09%
that means that in 1 hour Tim paint 9.09% of the fence

John and Tim in 1 hour can paint (11.11%+9.09%)-----> 20.2 %
so
20.2%---------> 1 hour
100%--------> X
x=100/20.2-----> x=4.95 hours

the answer is
4.95 hours