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A positive two-digit integer ab is a multiple of a+b. How many such integers are there?

 Sep 28, 2020
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10 , 12 , 18 , 20 , 21 , 24 , 27 , 30 , 36 , 40 , 42 , 45 , 48 , 50 , 54 , 60 , 63 , 70 , 72 , 80 , 81 , 84 , 90 , Total =  23 such numbers

 Sep 28, 2020

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