Average of two-digit numbers, which remain same when digits interchange their position is

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4.Average

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

A

$33$

B

$44$

C

$55$

D

$66$

Solution

Such two digit numbers are $11,22,33,44,55,66,77,88$ and $99 .$

Sum of these number $=11(1+2+3+…..+9)$

$=11 \times \frac{9}{2}(1+9)=11 \times \frac{9}{2} \times 10=495$

Average $=\frac{495}{9}=55$

Standard 13

Quantitative Aptitude

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