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Answers with some logic added in:

1)   2, 5, 7, 9, 75, 100      The magic number is 557

       557=500+55+2

             = 500+75-20+2

             = 500 +75 - 18

       557= 5*100 +75 - 2*9

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2)   4, 7, 25, 50, 75, 100    The magic number is 750

      750=100*7+50

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3)   4, 5, 7, 8, 25, 50       The magic number is 781

      781 = 785 - 4

             = 5 (   157   ) - 4

             = 5 (  200 - 50 + 7 ) -4

     781  = 5 ( 8*25 - 50 + 7 ) -4     

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4)   2, 3, 5, 6, 7, 8              The magic number is  945

      945 = 1000 - 55

      945 = 103 - ( 6*8+7)

      945 = (2*5)3 - ( 6*8+7)                          

OR

     factor(945) = (3^3*5)*7     Used the calc to get prime factors

     945 = 7 * 5 * 9 *3

     945 = 7 * 3 * 45

    if you used 7 and 3 like this then you have 2,5,6 and 8 to make 45.  

                                        45=48-3 = (6*8)-(5-2)

     945 = 7 * 3 * [(6*8)-(5-2)]                

OR

    945 =  7 * (5-3) * [(6*8)-3]                      

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Melody  Dec 29, 2015
 #1
avatar+10 
0

4^5-(25*8)+(50-7) = 781

1024 - 200+43 =781

1024-243 =781

kates  Aug 9, 2017

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