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  1. The unit digit in the sum of (124)372 + (124)373 is
    1. 5
    2. 4
    3. 2
    4. 0
Correct Option: D

As we know that
41 = 4;
42 = 16;
43 = 64;
44 = 256;
45 = 1024;
As we see that
Unit place of 41 = 4;
Unit place of 42 = 16;
Unit place of 43 = 64;
Unit place of 44 = 256;
Unit place of 45 = 1024;
Unit digit is repeating after every 4th index number.
Remainder on dividing 372 by 4 = 0
Remainder on dividing 373 by 4 = 1
∴  Required unit digit = Unit digit of (124)372 + (124)373
∴  Required unit digit = Unit digit of (4)372 + (4)373
as we know that Remainder on dividing 372 by 4 = 0 and Remainder on dividing 373 by 4 = 1
∴  Required unit digit = Unit digit of (4)4 + (4)1
∴  Required unit digit = Unit digit of of sum of ( 6 + 4 )
∴  Required unit digit = Unit digit of of sum of ( 10 )
∴  Required unit digit = 0



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