Question

The sum of the digits of a two digit number is $10$. When the digits are reversed, the number decreases by $79\%$ approx. Find the changed Number on reversing the digits.

• A. $91$
• B. $19$
• C. $73$
• D. None of these

Answer 1

Answer: (B)

$19$

If sum of digits is $10$ the digit can be $\to \{\begin{array}{c}10=9+1\to 1+9\\ 10=8+2\to 2+8\\ 10=7+3\to 3+7\\ 10=6+4\to 4+6\\ 10=5+5\to 5+5\end{array}$

Since number decreases on reversing possible sets are $\{91,82,73,64\}$

Now, let us assume $91$ be the number

On reversing it become $19$.

Decrease $\%=\frac{91-19}{91}\times 100\%$

$=\frac{72}{91}\times 100\%$

$=79.12\%$ ($79\%$ approx)

$\therefore$ Option B is correct.