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Aptitude Day 10

     
Answers of Day 9:      1. 6
                                     2. 5
                                     3. 0
                                     4. 0
                                     5. 6

The Cycle of Unit Digit:
  
Today we're gonna look at the cycle of unit digit 7.

     77
     7= 49
     7= 343
     74 = 2401
     7= 16807
     7= 117649
     77 = 823543
     78 = 5764801
     79 =40353607
     710 =282475249


If you notice the unit digit in all 10, you can see, it repeats. 7,9,3,1 (which Iā€™ve highlighted) then again 7,9,3,1and so on. 

So the cycle of unit digit 7 is

    7= 7 (if you get the remainder as 1)
   7= 9 (if you get the remainder as 2)
   7= 3 (if you get the remainder as 3)
   7= 1 (if you get the remainder as 0)

Example: Unit digit of the product of   726 * 731 * 791 =?

Solution:  Power/ 4. Since it has only 4 (7,9,3,1 ) in the cycle and it again repeats...

Power/4= 26/4. You will get the remainder 2 so the unit digit is 9
                31/4. The remainder will be 3 so the unit digit is 3
                91/4. The remainder will be 3 so the unit digit is 3

 9*3= 277*3=21. So the unit digit of this product is 1.


Problems to solve

1.    780*733 *746 =?

2.    711*7 =? 

3.    713* 719 * 749 * 751 =?

4.    764*718 *781 =?

Answers are here Aptitude Day 11







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