Both of my brothers and their families live in St. Charles-their last name is Walsh.
Anyway, the formula for working together is
time together + time together = 1
time alone time alone
t/40 + t/30 + t/24 = 1 Multiply both sides by the LCD, which is 120.
3t + 4t + 5t = 120
12t = 120 t = 10 minutes