Question 54544
Work: t/30
Work: t/40
Work: t/60
t/30 + t/40 + t/60 = 1
120t/30 + 120t/40 + 120t/60 = 120
4t + 3t + 2t = 120
9t = 120
t = 40/3 or About 13.33 hours