A charity bingo game costs 2 dollars per round and has a 13 dollars entry fee for an adult. It costs 3 dollars per round and a 10 dollars entry fee for a child. For how many rounds of bingo are the costs the same for an adult and a child?

Let r be the number of rounds. The adult’s total cost is 13 + 2r dollars, and the child’s total cost is 10 + 3r dollars. Set them equal: 13 + 2r = 10 + 3r, so r = 3. The costs are the same after 3 rounds, which is choice D.

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