### The average of the two-digit numbers, which remain the same when the digits interchange their positions, is-

A. 33 B. 44 C. 55 D. 66 Answer: Option C

### Solution(By Apex Team)

$\begin{array}{l}\text{ Average }\\ =\Large\frac{11+22+33+44+55+66+77+88+99}{9}\\ =\Large\frac{(11+99)+(22+88)+(33+77)+(44+66)+55}{9}\\ =\Large\frac{4\times110+55}{9}\\ =\Large\frac{495}{9}\\ =55\end{array}$

A. 20
B. 21
C. 28
D. 32

A. 18
B. 20
C. 24
D. 30

A. 10 years
B. 10.5 years
C. 11 years
D. 12 years