Question

It takes one crew 6 hours to clean an auditorium after an event. If a second crew helps, it only takes 3.5 hours. How long would it take the second crew, working alone, to clean the auditorium?

Answer 1

Answer: 7.5 hours

Step-by-step explanation:

rate of first crew is 8 hours

jobe done by first crew in 2 hours is 2(1/8)= 2/8= 1/4

job left is 1-1/4= 3/4

rate of second crew 10 hours

time need to finish...

10(3/4)= 10(7.5)= 7.5

7 hours 30 minutes to finish

Answer 2

Not sure if this is a trick question but, if it is asking how long it would take the second crew without the first crew i assume 6 hours? 
or maybe it is asking for how long it would take the second crew after the first crew
6-3.5
=
2.5 maybe?