Question 1128070
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Ron and Matt both bought postcards during their trip to New Zealand. At the end of the trip, they decided to trade. 
Ron traded half of his postcards for 9 of Matt’s postcards. After that trade, each of them has 21 postcards. 
How many postcards did Ron have before the trade? How many postcards did Matt have before the trade?
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<pre>
Ron gave half of his postcards to Matt and obtained 9 postcards from Matt.
As a result, Ron has 21 postcards.


    It means that before obtaining 9 postcards from Matt, Ron had 21-9 = 12 postcards,
    and it is HALF of that he had originally.

    Hence, originally Ron had 2*12 = 24 postcards.




Matt obtained half of Ron's postcards, i.e. 24/2 = 12 postcards, but gave to Ron 9 his postcards.


    Thus Matt increases the number of his postcards by (12-9) = 3 postcards, having finally 21 postcards.

    Hence, Matt possessed 21-3 = 18 postcards originally.


<U>ANSWER</U>.  Ron had originally 24 postcards.  

         Matt had originally 18 postcards.
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Can your 5-grader understand it ?