Find unit digits

Find unit digits end with the 2,3,7

Q1. Find the unit digit of (2517)78

As we see the unit digit of given number is 7 so

71 = 7

72 = 7 * 7 = 4 9

73 = 7 * 9 = 6 3

74 = 7 * 3 = 2 1

75 = 7 * 1 = 0 7

As we see in each multiplication we take the unit digit of previous calculated value and at the power of 5 we see that it repeats from power of 1.

= 78 / 4

= 2

we divide the power with 4 beacuse at the power of 4 we get the different unit digit . and as we see we get the reminder 2.

So 72 = 7 * 7 = 4 9

Unit digit is 9

For the number like (3261)n , (6515)n , (2516)n , (2480)n where unit place digit are 1,5,6,0 respectivelly then unit digit will be same .