Find the unit digit of (330 - 245).
1). 1
2). 3
3). 5
4). 7
We know, 35 = 243
We can write,
⇒ Unit digit of 330 = Unit digit of (35 × 35 × 35 × 35 × 35 × 35) = Unit digit of (3 × 3 × 3 × 3 × 3 × 3)
⇒ Unit digit of 330 = Unit digit of (729) = 9
Similarly, 25 = 32, 210 = 1024
We can write,
⇒ Unit digit of 245 = Unit digit of (210 × 210 × 210 × 210 × 25) = Unit digit of (4 × 4 × 4 × 4 × 2)
⇒ Unit digit of 245 = Unit digit of (512) = 2
∴ Unit digit of (330 - 245) = 9 - 2 = 7