SOLUTION: Working alone, it takes Kristin 11 hours to harvest a field. Kayla can harvest the same field in 16 hours. Find how long it would take them if they worked together.

So Kristin's havesting rate is 1 field per 11 hours or  or  

So Kayla's havesting rate is 1 field per 16 hours or  or  

Let the answer be x hours

So their combined havesting rate is 1 field per x hours or  or 

The equation comes from  +  = 

                        

Multiply through by LCD 176x

                    16x + 11x = 176
                          27x = 176
                            x = 
                            x =  hours

Edwin