It takes Destiny y 4 hours to file all the daily paperwork. It takes Susan 5 hours to file the same paperwork. If they work together, how long will it take them?

Answer: it will take them 2.22 hours working together.

Step-by-step explanation:

It takes Destiny y 4 hours to file all the daily paperwork. This means that unit rate of Destiny would be

1/4 per hour.

It takes Susan 5 hours to file the same paperwork. This means that unit rate of Susan would be

1/5 per hour.

If they work together, they would work at their own individual rates. This means that their individual rates are additive.

Let t represent the time it will take them if they worked together. Since their combined rate is additive Therefore,

1/4 + 1/5 = 1/t

9/20 = 1/t

t = 20/9 = 2.22 hours