Question 213105
1st crew does 1/13 of the work in 1 hr.
2nd crew does 1/16 of the work in 1 hr.
3rd crew does 1/22 of the work in 1 hr.
Together 1/13 + 1/16 + 1/22 = 176/2288 + 143/2288 +104/2288 = 423/2288 of the work in 1 hr. (2288 is the LCD)
2288/423=5.4... hrs it takes the 3 crews to do the job.
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Ed