The unit’s place digit is half the ten’s place digit in a two-digit number N. If we swap the digits, the number gets reduced by 18. The number N is _____.

Correct option is B

Solution:
Let the ten’s digit be x. Then the unit’s digit = x/2.
So, Original number = 10x + x/2 Swapped number = 10(x/2) + x = 5x + x = 6x
Given that swapping reduces the number by 18:
(10x + x/2) − 6x = 18
Multiply throughout by 2 to remove the fraction:
(20x + x) − 12x = 36 21x − 12x = 36 9x = 36 x = 4
So, unit’s digit = 4/2 = 2
Therefore, N = 42
Correct answer:
(b) 42