A student finds average of ten 2 - digit numbers. While copying numbers, by mistake, he writes one n

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A student finds the average of ten $2 -$digit numbers. While copying numbers, by mistake, he writes one number with its digits interchaged. As a result his answer is $1.8$ less than the correct answer. The diference of the digits of the number, in which he made mistake, is

A

$2$

B

$3$

C

$4$

D

$6$

Solution

Difference in average $=1.8$

Difference between the number and the number formed by inter changing the digits $=1.8 \times 10=18$

By Hit and Trial $\Rightarrow 53-35=18$

Number $=35 \Rightarrow$ Difference $=5-3=2$

Standard 13

Quantitative Aptitude

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