math
posted by alex on .
it takes janet 9 hours to do a task and it take jancie 10 hours to do the same task how long will it take both of them to do the task together

janet rate: 1task/9hrs
jancie rate: 1task/10hrs
combinded rate=1task/hr (1/9+1/10)
timecombined=1task/combinded rate
careful with the fractions. 
5 hrs