1.  A number consists of two digits whose sum is 11. If 27 is added to the number, then the digits change their places. What is the number ?
A. 47
B. 65
C. 83
D. 92

Answer: Option A

Explanation:

Let the ten's digit be x. Then, unit's digit = (11 - x).

So, number = 10x + (11 - x) = 9x + 11.

Therefore (9x + 11) + 27 = 10 (11 - x) + x 9x + 38 = 110 - 9x 18x = 72 x = 4.

Thus, ten's digit = 4 and unit's digit = 7.

Hence, required number = 47.