The difference between a two-digit number and the number obtained by interchanging the positions of its digits is 72. What is the difference between the two digits of that number?
Choose the correct option:
A) 4 B) 5 C) 6 D) 8 E) 9
Sol.   Let the ten’s digit be x and unit’s digit be y,   Then, (10x + y) - (10y + x) = 72 ⇔ 9 (x - y) = 72   ⇔ x - y = 8   Answer 8
<result>D</result>
The difference between a two-digit number and the number obtained by interchanging the positions of its digits is 72. What is the difference between the two digits of that number?