Question

 If 57 is raised to the 28th power, what must be the value of the units digit in the result?

Answer 1

57^28=14,604,811,593,991,510,424,147,435,018,807,634,286,571,929,892,001

last digit=1

50 digits

Answer 2

57^1's units digit = 7

57^2's units digit = 9

57^3's units digit = 3

57^4's units digit = 1

57^5's units digit = 7

Therefore, we can detect a pattern and simply need to apply 28mod4 (because the units digit cycles through four numbers), and since 28mod4= 0, we can tell that the units digit will be 7.