Question

Martha can rake the leaves in her yard in 4 hours.Her younger brother can do the job in 9 hours. How long will it take them to do the job if they work together?

Answer 1

36/13 hrs

Answer 2

how?

Answer 3

look in 1 hour matha does 1/4th the work
while her brother does 1/9th the work
so in one hour the work done is
1/4 + 1/9 =13/36
so total hours to do the work is its reciprocal 36/13

Answer 4

thank you Sriram