3rd grade math problem: How many round trip tickets?

Question

65 train tickets were sold between Lorb and Monroe. 43 were sold from Monroe to Lorb. 37 were sold from Lorb to Monroe. How many were round trip tickets?

Answer 1

If you add the 43 + 37, you get 80 which is obviously more than 65.  This is because the tickets that are round-trip are being "double-counted", by being included in both groups.  To determine this double-counted amount, subtract 80 - 65 to get 15 round trip tickets.

 

To verify:

 

Since the tickets from M->L include the round trip tickets, subtract 15 to from 43 to get one-way M->L tickets.  So this is 28.

 

Since the tickets from L->M include the round trip tickets, subtract 15 to from 37 to get one-way M->L tickets. So this is 22.

 

So total tickets is L->M one-way + M->L one-way + round trip, which is 28 + 22 + 15 = 65

 

If you found this answer helpful, please say thanks