Question

Charlie and Dasha are roommates, and they have a dog. If neither of them is home, they hire someone to watch the dog. charlie must go on business trips every 6 months while Dasha must go on business trips every 9 months. If they both just got back from business trips, how many months will it be before they need to hire someone to look after the dog again? Explain your answer.

Answer 1

9 months. The answer is in the question- no need for a math problem. If both of them just got back and Charlie has to go every 6 months, then Dasha still has 3 more months until she has to go on her trip. 
Hope that all made sense:)