20. Dorothy and Rosanne are baking cookies for a party. Working alone, Rosanne can finish the cookies in 6 hours. Dorothy can finish them in 8 hours if she is working alone. How long will it take them to bake the cookies if they are working together? Round your answer to the nearest hundredth if necessary.

Answer 1

Let's use the formula:

1 / time together = (1 / time1) + (1 / time2)

where time1 and time2 are the individual times for Rosanne and Dorothy.

1 / time together = (1 / 6) + (1 / 8)
1 / time together = 0.2667
time together = 3.75 hours

Therefore, it will take them approximately 3.75 hours to bake the cookies if they are working together.