1.  A certain number of two digits is three times the sum of its digits and if 45 be added to it, the digits are reversed. The number is :
A. 23
B. 27
C. 32
D. 72

Answer: Option B

Explanation:

Let ten's digit be x and unit's digit be y.

Then, 10x + y = 3 (x + y)

⇒ 7x 2y = 0 -------- (i)

⇒ 10x + y + 45 = 10y + x

⇒ y x = 5 ------------- (ii)

Solving (i) and (ii), we get : x = 2 and y = 7.

∴ Required number = 27