Subject: General Aptitude · Chapter: Number System · Exam: 2007 · Marks: · Difficulty:
The digit in the unit's place of the number $123{ }^{99}$ is
(a)1
(b)4
(c)7
(d)8
Answer
Answer (as printed): C
Explanation
$3^{4}$ gives unit digit 1. So, $\left(3^{4}\right)^{24}$ gives unit digit 1. And, $3^{3}$ gives unit digit 7. $\therefore \quad 3^{99}=\left(3^{4}\right)^{24} \times 3^{3}$ gives unit digit $(1 \times 7)$ i.e. 7.
Explanation as extracted from the printed page; notation may be imperfect.