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Reverse Plugging In: Not Sure In Which Direction To Go

Mary and Nora have an equal number of marbles. If Nora gives three marbles to Mary, Mary will have four times as many marbles as Nora. How many marbles do Mary and Nora have altogether?
Incorrect. [[snippet]] This is the number of marbles Mary and Nora each have. You've fallen into the trap! What did the question ask?
Incorrect. [[snippet]] Eliminate this option. If Nora has 3 marbles, then she will have no marbles if she gives three marbles to Mary.
Incorrect. [[snippet]] Start with the middle option. If Mary and Nora have 8 marbles, then they have 4 marbles each. Thus, if Nora gives three marbles to Mary, then Nora would have 1 marbles and Mary would have 7. Since 7 is _not_ four times 1, this is not the correct answer. __POE__ and move on.
Correct. [[snippet]] If Mary and Nora have 10 marbles, then they have 5 marbles each. Thus, if Nora gives three marbles to Mary, then Nora would have 2 marbles and Mary would have 8. Since 8 is four times 2, this is the correct answer.
Incorrect. [[snippet]] If Mary and Nora have 12 marbles, then they have 6 marbles each. Thus, if Nora gives three marbles to Mary, then Nora would have 3 marbles and Mary would have 9. Since 9 is _not_ four times 3, this is not the correct answer. __POE__ and move on.
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