<em>Your answer is FR. </em>
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<em>"Fixed Ratio"</em>
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<em>I hope this helps. </em>
Answer:
Explanation:
While every case is unique, the most common causes of train accidents include: Negligence. Human error. Reckless pedestrians and drivers.
...
Negligence. ...
Human Error. ...
Reckless Pedestrians & Drivers. ...
Mechanical Failure. ...
Speedy Trains. ...
Defective Tracks. ...
Derailments. ...
Unprotected railroad crossings.
Answer:
2.22 hours
Explanation:
If Sally can paint the office by herself in 5 hours, we can say that in one hour she paints 1/5 of the office.
On the other hand, Lucy paints the office in 4 hours, which means that, in 1 hour she paints 1/4 of the office.
Therefore, to know how much they would paint per hour working together, we are going to sum up the fractions they paint per hour:

Therefore, working together they will paint
of the office in one hour.
Now we can establish a rule of three: if they paint 0.45 of the office in 1 hour, how long (x) will it take them to paint 1.0 of the office?

And therefore 
Therefore, it will take them 2.22 hours to paint the office working together.