Find the ones digit of 73^353
Find the ones digit of 73^353
Answer/Solution
3
Steps/Work
The units digit of 73^353 will be the same as the units digit of 3^353.
3^1=3 --> the units digit is 3;
3^2=9 --> the units digit is 9;
3^3=27 --> the units digit is 7;
3^4=81 --> the units digit is 1;
3^5=243 --> the units digit is 3 AGAIN;
...
So, as you can see the units digit repeats in blocks of 4: {3, 9, 7, 1}, {3, 9, 7, 1}, ... Now, since 353=352+1=(multiple of 4)+1, then the units digit of 3^353 will be the first number in the pattern thus 3.
Answer:A.
3^1=3 --> the units digit is 3;
3^2=9 --> the units digit is 9;
3^3=27 --> the units digit is 7;
3^4=81 --> the units digit is 1;
3^5=243 --> the units digit is 3 AGAIN;
...
So, as you can see the units digit repeats in blocks of 4: {3, 9, 7, 1}, {3, 9, 7, 1}, ... Now, since 353=352+1=(multiple of 4)+1, then the units digit of 3^353 will be the first number in the pattern thus 3.
Answer:A.