# Practice Questions on Number SystemAptitude Questions and Answers

## Easy Number System Question - 16

 Q16. $(AA)^2 = DCBA$, where $A$, $B$, $C$ and $D$ are distinct digits with $B$ being odd. Find the value of $D$.
 A. 4 B. 6 C. 1 D. 1 or 4

## Easy Number System Question - 17

 Q17. What is the last digit of the number 3579+ 1?
 A. 1 B. 3 C. 4 D. 7

## Easy Number System Question - 18

 Q18. If $x$ and $y$ are any natural numbers, then which of the following is an odd number?
 A. $x^y + y^x + (x-y)(x^y + x)$ B. $x^y (x + y)(x^y + x)$ C. $y^x (x^y – y) (x^y - x)$ D. None of these

## Easy Number System Question - 19

 Q19. A and B are playing mathematical puzzles. A asks B "which whole numbers, greater than one, can divide all the nine three digit numbers $111, 222, 333, 444, 555, 666,$ $777, 888$ and $999$?" B immediately gave the desired answer. It was:
 A. 3, 37 and 119 B. 3, 37 and 111 C. 9, 37 and 111 D. 3, 9 and 37

## Easy Number System Question - 20

 Q20. Two prime numbers $A, B(A < B)$ are called twin primes if they differ by 2 (e.g. 11,13,or 41,43....). If A and B are twin primes with $B > 23$, then which of the following numbers would always divide $A+B$?
 A. 12 B. 8 C. 24 D. None of these
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